However it's problems became well known. The transmission was very prone to breaking, the gun wasn't properly centered so the turret couldn't rotate if you tilt it by parking the tank on a slope and shooting while moving could dislocate the turret. The tall, slow tank that had to shoot while staying still was an easy target. Don't forget T-34-tier navigation tools.
A year later, just like the KV-1, the tank was almost invulnerable to German early war AT weapons except 88 mm Flaks. Random types of ammunition like shrapnel and anti-concrete were often used due to shortages. In the end, almost all of 204 KV-2 tanks were lost in 1941.
As silly and excessive the project was, if that 152 mm explosive somehow managed to hit any tank it instantly killed the crew and dislocated the turret often outright sending it flying. KV STRONK!