Holy crap that was a big explosion for a drone impact!

My guess from the video and the explosion is that the drone charge penetrated and detonated all 22 onboard shells in the magazine inside the tank. The notable “improvement” of T-90 over T-80 and before is that the magazine is located in the back of the turret instead of in a carousel under the turret. However, T-90 doesn’t have the same blow out panels in the turret magazine that western tanks do that direct exploding onboard ammo outside of the tank. The T-90’s exploding ammo goes right into the crew compartment.