I've seen my share of fire around metal and the amount of steel on those things the fire shown on the picture doesn't do much. Of course all the plastic on hoses/wiring, seat covers and things like that, the crew obviously included, wouldn't be fine. You obviously couldn't just hop in and drive the thing off from that point and if your task was just to disable the tank and trust that you have the area under control so that it couldn't be recovered for repairs any time soon, sure, the first drone would have been well enough.

I don't really know either, but based on the videos from the lines it seems like Ukraine gladly spend few cheap drones to make absolutely sure that the things they stop won't move again. Additionally, some models, even if their crew is dead and the engine is dead, can still autonomously respond to incoming fire (assuming of course that there's still juice in the batteries and the weapons systems work), so that alone for me is enough to spend another drone to confirm that the thing is dead and stays that way.