While you wait for a more targeted answer, you might be interested in some threads from the FAQ section on "Post Tramatic Stress Disorder before the modern era" as well as a recent search:

General

• How did the soldiers of antiquity/medieval times deal with the inevitable PTSD type issues that come from brutal hand to hand combat? - 147 comments, over 1 year old.
• More examples from all across time, with analysis and source criticism present in several of the comment threads.
• Was PTSD any more, or any less, prevalent amongst ancient and medieval soldiers than todays soldiers? - 16 comments, over 2 months old.
• This thread delves into a discussion of the merits and flaws of an often cited work on PTSD amongst pre-modern warriors.

Ancient

• Did Ancient peoples suffer from Post-Traumatic Stress Disorder or similar psychological issues? - 55 comments, over 2 years old.
• There's a wealth of examples drawn up in this thread though not as much analysis.
• Is there any information on Post-traumatic Stress in societies in which warfare was looked at in a more favorable light (e.g Sparta)? - 41 comments, over 2 years old.
• The topmost comment draws examples from the thread above this, but down below there's a source brought in to analyze pre-modern combat which results in a debate both about such occurrences and the value of the source.
• Are there any indications of combat PTSD in societies like the Spartans, Khan's or Alexander's armies? - 31 comments, over 1 year old.
• This thread narrowly focuses on Roman soldiers and thus is able to do strong analysis of the available texts and evidence in a way not done in the threads above.
• Is there evidence of PTSD in ancient warrior cultures? - 14 comments, over 1 year old.
• A few more examples ancient examples as well as dealing with a book on the topic of PTSD.
• Did men of the past suffer emotional trauma from war and killing? - 6 comments, less than 1 month old.
• This thread goes deep into the source criticism and interpretation when making judgements of whether or not pre-modern peoples were experiencing what would be diagnosed as PTSD in the modern day.

Medieval

• Did soldiers in the middle ages get PTSD? If so, was it different then PTSD now? - 83 comments, over 2 years old.
• There's some debate in this thread whether or not the circumstances that people lived in during the Middle Ages made them more resilient or not to PTSD.
• Is there any mention in medieval books and records from those times of what we now call PTSD in knights, soldiers, warriors etc? - 9 comments, less than 1 month old.
• There's one large quote given in this thread about how clergy specifically cited the psychological toll of combat as a reason against it.

Early Modern and Modern

• How was PTSD (Post-Traumatic Stress Disorder) treated in the Middle Ages of Europe (or anywhere during 400A.D. to 1500A.D.)? How well documented are we upon the subject? - 26 comments, over 10 months old.
• Despite the title, this thread focuses on Early Modern Europe and also deals with the difficulty of retroactively diagnosing people through their writings.
• How common was PTSD in 18th and early 19th century armies? Particularly in Napoleon's armies - 4 comments, over 11 months old.
• One commenter talks about a high level officer who may have experienced PTSD such that it impacted his decision making at a critical moment in a major battle.

But how come it truly became a thing during late world war 1 I mean what caused it to be such a common thing in WW1 compares to all the other thousandso of years of warfare

This question is being downvoted (because it's asked so often) but it really is not a stupid question by any means and it has a very simple answer actually: WWI was separated from its previous conflicts because, as many historians theorize, it was one of the first (if not the first) wars that was truly, for its entire duration, constant fighting and struggle.

Think about this for a moment. Offensives before were relatively brief; the Hundred Years' War for instance had like, what, half a dozen significant non-skirmishes? Even as the general tempo of warfare picked up into the Napoleonic Era it still was more or less following that pattern: You march, you fight a battle in the morning into the afternoon, by night it's mostly over and you spend the fireside in relative peace with your buddies.

There are many terms for this, the one I hear often is 'fireside therapy'; that is, the fact that pre-modern soldiers (in the general) had the luxury to fight a battle in the day and then relax and share a fire with their comrades in relative peace and, many times, not have to worry about fighting another battle for weeks if not months or years, was crucial to their mental health. It becomes a lot easier to deal with the realities of war and the horrors of killing if you do it once or twice a year for a total of a few hours and spend the rest of the time just killing time.

While the Napoleonic Wars, again, saw great change to that it still fit that mold significantly enough and we see a gradual shift to this throughout the rest of the 19th century; yet it fully comes into form in its worst state in WWI. Men aren't fighting a battle on an evening and then both sides retreat and maneuver around eachother for a few weeks and get that kind of relative peace; they beat back an enemy offensive movement and tens of thousands more will be coming the next day, and then the next, and then the next. When the offensive ends it doesn't matter they need to stay on the front. They get no reprieve they get curling up in a ball in a trench being shelled endlessly for days if not weeks all while fighting battles and skirmishes alike.

So it's not like PTSD didn't exist before WWI it's just that, by the structure of war due to social and technological limitations, men generally had greater time to cope with their issues. By WWI with mechanized, industrious warfare and constant fighting across a front and men becoming near disposable with millions more in reserve they dont' get that 'fireside therapy'. They get "Welp we held off the Prussians today but tomorrow another battalion will hit us and another 2500 shells will hit our position, enjoy your night of sniper fire and machine guns whizzing over our trenches."

In other words they had no time during the war to internalize it and bond with it with their mates; they just spent it all fighting and dying and only after the fact with all the mental issues compounded up, especially things like survivors guilt, it all crashes down on them at once. All of that emotional baggage that would have been before alleviated every night or at least every other night through relative peace by a fireside that just wasn't for 2-4 years crashing down on them all at once.

But how come it truly became a thing during late world war 1 I mean what caused it to be such a common thing in WW1 compares to all the other thousandso of years of warfare