My guess is that the top hatch was open and the guy was thrown out by the "main" blast ahead of the fireball. Doubtful he made the escape himself, the initial blast would have incapacitated him at least momentarily. Anyway, before he hit the ground everyone else was already charbroiled meat on the walls. The initial hit happens at 0:58, secondaries start at 1:02ish with smoke coming from the main gun too (without it even being fired). At 1:05 it looks like the entire autoloader's ammo carousel detonates at once (and the ragdoll hits the ground), instantly cooking a tank-sized KFC meal. Remember that T-72 does not have compartmentalized ammo storage or blowout panels or the like, so top hits will most often penetrate directly into the autoloader's ammo carousel that's under the crew (horizontal hits are less likely to do this at once). Of course, the crew who were in the way of the blast wave that set off the ammo were dead even before that. Also, some extra ammo is commonly stored around the turret and hull as well, and those will go off much easier in any penetration (could be that these go off at 1:02, and then detonate the main storage).
In-depth analysis here:
http://www.liveleak.com/view?i=efb_1359418903"Slowly burning to death" does not fortunately happen (what you see later is the fuel and MG ammo catching fire, everyone still inside is already dead at that point) in a tank with non-compartmentalized ammo bays.
