A lot of both. As the Panzermuseum Director said in my video, the German reaction to the rapid success in France was “Huh. That shouldn’t have worked. Oh well.” They actually expected a longer fight than they got.

There are some misconceptions. Actually, a lot of misconceptions.

The first one was that the Maginot line failed to work. It actually worked perfectly. Its intent was to encourage the Germans to go North, away from the French industrial areas. Better yet, away from France. Belgium looked like a great place to settle their differences, which obviously did not enthrall the Belgians, leading them to aggressively pursue their neutrality until far too late. And, of course, the Germans did go through Belgium. There was a good thrust through the middle, and a daring attack on the Belgian fortress of Eben Emael broke the back of the Belgian defensive line off the bat. And, of course, there was the strong thrust through the Ardennes.

It wasn’t that anyone thought the Ardennes was impenetrable. They just thought it would take the Germans a bit longer to get through than they actually did. Even at that, there was some tough fighting, and the German traffic jams would make Los Angeles at 5pm look kind of relaxing.

Another misconception, that the French has better tanks, badly used. They actually had pretty lousy tanks, and a lot of them were used quite sensibly. They were simply outfought and out maneuvered.

The breakthrough came at Sedan, and was something of a close-run thing. If you look at it at the lowest levels, you’ll see that the French did not just roll over, and it was some actions by a couple of extremely low-level units at a couple of key locations which made the difference. It could very easily have gone the other way. However, the Germans were very, very good at exercising local initiative and taking advantage of any lucky breaks which came their way. That was what made the impressive German achievement. It could be taken to extremes. Rommel did the “you are breaking up, I can’t hear you” routine, which would have gotten him court martialled had it not worked. But it worked. Similarly, the local aviation commander ignored instructions on the air attack on the Sedan defenses.... but it worked.

Once they had established their toehold on the far side of the Meuse, and made sure to defend the bridges with incredibly heavy air defenses (another plus in the German column for planning), it became the French fight to lose.

The French doctrine was far more inflexible insofar as operational level tactics were concerned. Co-ordination and Artillery was everything. Compared to the Germans, it was night and day, but that doesn’t necessarily mean it was wrong. The Germans that met the French operating correctly, such at Gembloux, did not in any way enjoy the experience. The problem occurred when the doctrine did not operate correctly, and this became the French Military failure.

In order to tightly co-ordinate the battle, French commanders tended to rely heavily on communications, and out of a stupid fear of eavesdropping, they wouldn’t use radio. That left just telephones and messengers. Wires would get cut, messengers would get lost or killed. This meant that often times by the time the French commanders figured out what was going on, the situation was overtaken by events. Worse, commanders often waited for orders. In one case, a commander refused to move until written orders arrived, even though his staff had been notified over the telephone as to what those orders would contain, when they got there three or four hours later. From when a “move” order was given to when movement started happening could take 16 hours, whereas for the Germans, it could take 16 minutes.

This is where the Germans got lucky. Had they been facing a competent enemy command structure, (or even the one they faced, just which bothered to use the radio more) they could well have been kicked back across the Meuse. However, again and again, French forces were ordered to occupy and hold defensive positions which, when they finally got there, they discovered that the Germans had gotten there only just before them simply because it took so damned long for them to do anything. The accounts from the senior British officers who visited French command posts were such that they literally shook French commanders into action. This, this, was the French military failure.

Once the Germans had cut the French line, they also cut off the best of the French mobile forces. They, of course, ended up in the Dunkirk pocket. The rest of France was basically held by second-string forces.

The Germans were right, it shouldn’t have worked. The French could likely have held them, notwithstanding the rapidity of the Ardennes thrust. The French soldiers fought hard (until the Panzer panic struck), but were let down by their C2 structure.

For further reading, I highly recommend Col. Dr. Karl-Heinz Frieser’s “The Blitzkrieg Legend”