Edit: Among the above is the misconception of the battle of France; that German armors was more and better than the French - this was wrong. What was the German advantage in tank warfare during the invasion of France was neither their superior tanks nor their numbers. Just their doctrine. French spread their more numerous and better tanks to support infantry divisions, when the Germans used them in huge formations to create spearheads.
This is a common myth. In point of fact, the French attempted multiple divisional attacks with armored formations and their doctrine absolutely did encourage the use of massed armor. And in fact the very man who chose to disperse those armored divisions in the area of Sedan was the single most experienced armored leader in the French army, a major proponent of the massed armored attack and the man who literally created the French armored forces (and had a major hand in the design of the best French tank, the Somua S35) : General Jean Flavigny. If you're looking for the French Guderian, this is the guy.
Here's why he made that call in his own words:
The key decision, nevertheless, was the halting of the attack. In his postwar letter to the National Assembly, General Flavigny explained why he halted it." The general situation had completely changed. The 55th Division which could have supported my units in the morning no longer existed as a fighting unit. The 5th Light Cavalry Division held the woods of Mazarin [to the northwest of Mont Dieu] with difficulty. The enemy had had the entire morning to cross the Meuse and to send reinforcements to the south of the river. It seemed impossible to make the counterattack…before night…. An attack led by weak, poorly trained troops seemed to me to be doomed to a failure that could have compromised the defense of Mont Dieu
And part of why he made that call was a frankly embarrassing training exercise he saw a week prior:
Another important factor was Flavigny's lack of confidence in the French armored divisions. In a long account of his experience in the campaign, he described an exercise of the recently formed 2nd Armored Division on 8 May 1940, in which it had been ordered to conduct a counterattack that, according to General Flavigny, did “not correspond to the employment of a mechanized force in a rapid engagement.” In other words, the division received a fairly simply mission to accomplish, but it took more than four hours to move four kilometers and arrived “completely” disorganized. Flavigny concluded, “I had doubts about having to employ a unit so poorly trained.” Less than a week later, he faced exactly that decision and clearly was influenced on 14 May by his memories of the poor performance of the armored unit in the training exercise
Both are from The Breaking Point by Robert Doughty.
French pre war training was frankly atrocious and I could go into book length level of detail about how troops expected to drive the B1 were trained solely on the FT17 if they were lucky. Many reservists simply held up signs that said "tank" and walked around while in training for armored maneuvers, or if infantry were given only four rounds _a week_ of rifle ammunition for firing training. I'm dead serious, and you can verify it in Arming Against Hitler by Eugenia Kiesling. The French army had tons of modern kit by the time the way started, but the vast majority of it was produced in the year prior and many soldiers in specialist roles had never used or even seen the equipment they were supposed to be experts on before being handed it and sent off to war.
There was also an incredibly unhelpful culture of not admitting the massive issues within the army as it was believed that doing so would only provide succor to the enemy and hurt the prestige of the army and the morale of the citizens. Complaining about the bureaucratic morass that everyone was mired in (routine maneuvers could generate three inch thick piles of paperwork and require approval from senior army leadership) or the dire state of training (barely trained conscripts training reservists who were expected to bring front line units to full strength) were seen as good ways to end your career: if you complain that you can't get the job done with the shit sandwich you've been given, it must be because you suck, not because the army is insane. You can read account after account of pre-war French officers bemoaning the many failures of their army in private while fiercely attacking any suggestion that it was not the best in the world in public.
A final point. At every decisive moment in the Battle of Sedan it was German infantry, not armor, leading the way and crushing French resistance. Both Doughty and Karl-Heinz Frieser give German infantry the credit for the impressive tactical successes of the German army. At the operational level certainly the armor was decisive, but the breakthroughs were fought and won with incredible courage and skill by the infantry.
I don't generally compliment the German army in WW2, so that really is saying something.