I believe this is obvious and I’ll try to keep it short; tanks don’t instantly brake when they’re destroyed. They just keep going until something hits the brake, they run out of fuel or the engine/transmission is destroyed.
There have been countless cases of vehicles driving around with the crew dead inside, and in my opinion, it’s a realistic aspect the game lacks.
In case the driver is “unconscious”, you could probably just make the tank slow down without fully braking after it’s destroyed, (simulating how the driver would stop step on the accelerator), but on the other hand, if the vehicle is knocked out with the driver surviving then the braking would be justified, in order for the driver to abandon the machine.