It seems to me that in the interwar period there were a lot of tanks designed with the idea that they would stay with groups of infantry, providing direct fire support while being a lot more durable than a field gun. My understanding is that this was generally abandoned in favour of faster tanks which operated somewhat independently of infantry. But to my very limited knowledge, the infantry tank seems to make sense. What were the theory’s disadvantages? (Or is my understanding flawed?)
Tanks are at their best when they can maneuver quickly. It’s hard to do that if there are friendly infantry close by. On top of that, being too close to a tank is dangerous for infantry. The tank is going to be drawing fire from many sources, and basically every time the armor gets hit there’s going to be shrapnel flying off the body of the tank. Bullets bounce, and a lot of modern armor platforms use reactive armor which explodes when hit.
Infantry and armor units absolutely train to cooperate, but it’s extremely hazardous for infantry to be very close to a tank during a battle.