There were a couple of reasons, but there is certainly a misconception that the Italian Army were useless and ineffective. When the British lost, they were happy to blame the Germans and not advertise that it was Italians that beat them, when the Germans lost, it was easier for them to say that they were let down by their allies than beaten. Case in point, many Americans are familiar with the reversal that they suffered at Kasserine Pass, the first time they fought the Germans in a major engagement. Not so commonly known is the fact that the unit which broke the American lines (after a German failed attack) was in fact Italian. The majority of the Axis forces in North Africa was Italian, and -something- was preventing the British from just waltzing over the desert. It wasn't just the 80,000 Germans in the Afrika Korp.

That said, the reputation is not without a background of truth. The first problem was equipment related. Italy simply didn't have a significant arms industry. They made some excellent designs, notably with ships and aircraft, but when it came to ground combat, the really good stuff like their 90mm (better than the German 88) couldn't be built in numbers, and though their tanks and artillery were perfectly good by 1940 standards, they never really got updated to hold their own against the next generation of vehicles coming from the U.S. or USSR.

The next problem was of effectiveness. Put simply, some units were great, and others were utter wastes of resouces. There was a lot more variety in the field in quality for the Italians than some countries. There were also motivational issues. The Italian soldiery simply didn't buy into the whole reason for fighting the war. They did their duty, usually, but that was it. Some units had officers and enlisted who did not get on well, aristocratic officers leading peasants, and the officers would treat them as such.

As a result, finding units which were both well motivated -and- well trained such as Bersaglieri, the armored divisions, or some artillery units, could be difficult. That said, Rommel announced that if well-led, the Italian fighting man was as good as any other.

Finally, there were some logistical matters. You can imagine what was a common ration in the Italian Army. Pasta. Cooked in.... Water, that resource not commonly found in deserts. Frequently logistical equipment was appropriated or prioritized for the Germans as well, which wouldn't have helped unit effectiveness.

I can't answer all of your question but just to make some things clear, Italy wasn't weak and ineffective in WW1, in fact they gave the Austrians a very hard time and Conrad Von Hotzendorf was also very concerned about the Italian Front, and you should also consider that ultimately the Italians defeated the Austrians at Vittorio Veneto.

They did have some setbacks, most notably some of (not all) their equipment was outdated, their Chief of Staff, Cadorna, who wasn't very good to say the least and had some rather tyrannical methods, the troops' morale as the Italian command found out after Caporetto when 400,000 troops deserted and last but not least Italy hadn't completely industrialised yet like Russia.

Despite these problems it should be noted that Italy was by far not the weakest link, since it fared better than a number of allied countries like Romania, Russia or Serbia which all eventually backed out of the war or, like in Serbia's case, were occupied even if their army continued to fight. Also, up until the Germans sent the Austrians a few of their own Alpenjaeger divisions, the Italian Alpini (and the main army) not only were holding their ground but were also making gains, albeit at a slow pace.

i'll copy and paste some of my previous answers in some other threads explaining this, but the way in which many people (and many historians too) remember Italy's performance in WW2 is result of misinformation and wartime propaganda which has since been accepted as fact. Yes, in both wars Italy did face several decisive defeats, however there is a much broader context to each of these scenarios that need to be considered for someone trying to argue that Italy's performance in either war as "weak and ineffective."

In WWI, there is nothing to suggest that Italy performed any more poorly than Austria-Hungary (or any nation in WW1 for that matter). WW1 was a conflict of 19th century military doctrine with 20th century weapons. I would find it difficult to argue any nation was "strong and effective" in WW1, and any belligerent could certainly be considered a weak link. The problem is, Italy is often a scape-goat. The Italian front was in arguably the harshest terrain of the entire war. High-altitude fighting, 12-separate offensives on the Isonzo Valley, many of which taking place for control of key positions on mountain-tops. It was basically deadlocked, with the Italains slowly making some advances until the Germans conducted an offensive along with the Austro-Hungarians, at the infamous Caporetto. Like the Italians, the Austro-Hungarians were also over-extended. The offensive likely would have failed had it not been for German reinforcements (and leadership). The Italians who were unable to reinforce their lines in the rapid advance of the Central Powers lost significant amount of land, and for the first time Venice became seriously threatened by siege. So the Entente sent several divisions to help stable the lines, which gives Italy this reputation of requiring assistance, but the Italians had already halted the offensive when they defended Mount Grappa, a strategic fortification on a key mountain top. What also isn't really well known is that Italy made a remarkable reformation as a result of this, was able to rapidly mobilize a sizeable army and began a series of counter-offensives (with very minimal Entente assistance) that began to put the Central Powers on the retreat for the remainder of the war. It's important to note that the change in leadership was also a significant aspect to Italy's miltiary reformation, replacing the very inept Luigi Cadorna with Armando Diaz, a very competent military commander.

Now, as far as WW2 is concerned, Italy received a poor reputation largely due to propaganda during the war which has since been taken as fact, which came about during 'the parallel war,' the conflict in North Africa before any German or American involvement. 300,000 Italians were far too over-extended in the initial invasion into Egypt and were defeated by 30,000 British forces (and several hundred thousand Askari troops which are often ignored) who had tanks and superior air forces. These arent things that people like to take into account, all they see is 300,000 Italians defeated by 30,000 British and pushed back into Libya. Now there is a lot that Italy dropped the ball on WW2. Early (and devastating) naval defeats severely crippled the Italian Navy. They were eventually able to even the odds (which I will detail below), but it remains as some severe command errors by the Italian command. The invasion into Greece was also poorly conducted. The Italians had a habit of invading sovereign nations with no armor support. They eventually sent in the Centauro armored division but they were largely composed of L3 tankettes, and were easily capturable and not very effective. So a lot of the criticisms of Italy during WW2 is very accurate, but in most cases it is a lot more complex than to just say they are inferior or a weak link. I will copy/paste many marginal success of the Italian military from some other posts I made:

There were many instances of not only stubbornly fought military actions, but also successful engagements by Italian forces in WW2. I should first establish the strong military tradition that surrounds the young Italian nation. When she was formed, there are several elite branches that serve different purposes, and Italy's geography is the key in explaining this otherwise overlooked phenomenon. The Italian Alpini are specially trained soldiers for mountain warfare. Comparable to German Gebirgsjaeger or the US 10th Mountain Division, they have a very unique history of traditionally defending Italy's northern border which is protected by the Swiss Alps. Italy is also a Peninsula, so the Mediterranean sea is the border and to secure it, a strong navy is needed. The years between WWI and WWII, Italy built up her navy at a very rapid rate and in the 1930's, she had gained the status of 4th largest navy in the world. To sum up Italy's achievements in WWII, I think a fair assessment would be, "performing well in desperation." Though they may not have always been the victors, the hard fought battles of many Italian forces deserve to be recognized.

Examining Italy's Navy (La Regia Marina) alone proves the bravery and sacrifice of many Italians during the war. Early in the war, the Italian navy faced a series of set backs. The British surprise raid on Taranto harbor putting 3 battleships out of action, followed by the staggering defeat at the Battle of Cape Matapan essentially gave the British naval superiority overnight. At such a disadvantage so early on, Italy began to experiment with less conventional methods of warfare. The Xa Flotiglia MAS was a special forces division of the Italian army. the expeditions of the submarine Scire and Junio Valerio Borghese conducted Frogmen raids on various British ports throughout the Mediterranean. The most successful raids were at Gibralter and Alexandria, in which these soldiers piloted torpedoes, completely submerged, and attached them to ships hulls with a timed fuse. The most notable damage they did was sink the HMS York and Queen Elizabeth, but they also destroyed hundreds of thousand tons of British shipping this way. The Frogmen of Xa MAS were the direct inspiration for the US navy seals. Also, the disadvantage at sea faced by the Italians obviously had detrimental affects on Italy's ability to ship supplies to the soldiers in Africa. Many accounts claim sailors surviving brutal attacks, and finding themselves facing more attacks on the very next mission. the Royal navy's naval superiority made it nearly impossible to protect Italian supply ships, even still, ~79% of Italian shipping was delivered which is a testament to the valiant effort put forth by Italian sailors. the book, Italian Navy in World War II by James Sadkovich provides exact figures:

"WAR MATERIAL TRANSPORTED FROM ITALY TO LIBYA SINCE JUNE 1940 TO JANUARY 1943 (expressed in tons):

Combustible oil: left:599,337 arrived:476,703 (80%)

Vehicles & spare parts: left: 275,310 arrived:243,633 (88%)

Fire-arms & munitions: left: 170,060 arrived: 149,462 (88%)

Other cargoes: left:1,200,673 arrived:1,060,157 (86%)

TOTAL left: 2,245,380 arrived: 1,929,955 (85.9%)

ITALIAN-GERMAN PEOPLE TRANSPORTED FROM ITALY TO LIBYA SINCE JUNE 1940 TO JANUARY 1943:

left: 206,402 arrived: 189,162 (91.6%)

WAR MATERIAL TRANSPORTED FROM ITALY TO TUNISIA SINCE NOVEMBER 1942 TO MAY 1943 (in tons):

Combustible oil: left: 132,522 arrived: 94,472 (71%)

Vehicles & spare parts: left: 73,870 arrived: 59,440 (80%)

Fire-arms & munitions: left: 92,149 arrived: 62,806 (68%)

Other cargoes: left: 127,628 arrived: 89,814 (70%)

TOTAL: left: 433,160 arrived: 306,532 (71%)

ITALIAN-GERMAN PEOPLE TRANSPORTED FROM ITALY TO TUNISIA SINCE NOVEMBER 1942 TO MAY 1943:

left: 77,741 arrived: 72,246 (93%)," (Sadkovich: 1994)

Now, with regards to military actions on land, I want to return attention to the Italian Alpini I briefly mentioned above. As Hitler invaded the Soviet Union, Mussolini wanted to support his trusted ally by sending hastily assembled divisions to assist in the new front. Mussolini initially sent 62,000 men at the beginning, and continuously reinforced the ARMIR (Italian Eigth Army) until it hit its peak at 227,000 soldiers, of which 4 Alpini divisions were formed. Now, keep in mind, Alpini are specially trained for mountain warfare. There's no mountains near the Don river where they were positioned, so their role was entirely unorthodox for their standard doctrine.

We all know the story of Stalingrad and the encirclement of the German 6th Army. The initial Soviet plan was to hit the Italian and Hungarian troops on the flanks to encircle the Axis at Stalingrad, so it was the non-German forces that were tasked with defending the flanks from massive armored Soviet offensives, and they had little more than out-of-date AT guns and Molotov cocktails to stop them. As the noose tightened, the Axis began a desperate retreat back to the stabilized lines in Ukraine. The march back was a massive line composed of Italian, German, and Hungarian survivors that were constantly harassed by Russian armored and motorized divisions. It was the Italians that successfully repulsed the Russians at the Don that had the most unit strength (in terms of numbers) of the Axis forces. So it was the Italians that defended the rear and spearheaded the breakout attempts. This is a very difficult job for an army that has already suffered staggering casualties. This situation is where the 2nd Alpini Tridentina division made its fame. The Tridentina famously led the column through several well-defended Russian towns, and are credited with the break out of the encirclement, leading thousands of Axis stragglers to safety. Josef Stalin himself claimed that the Italian Alpini were the only Axis force he could not fully defeat.