Probably cought by surprise, by the time they had to react they were already souranded and every window or door were shot at or through, like the video someone posted here, they might also have studied which time soldiers go inside so they attack at that time like prayer times or eating time...
What about aps, vt4 suppose to have that, does our version have that too, it's the most defining features that makes it different from ak1 and other older tanks.