A typical RPG is fairly dinky, and it hit on the turret, one of the most heavily armored parts of the tank. There is a surfeit of much better antitank weaponry out there, which is why tanks are on the downside until somebody can invent a better way to protect them.
Yep, this hit by a new Israeli missile on a Syrian tank coming across a field is pretty spectacular
http://www.youtube.com/watch?v=LCXKTTOpJQ4
as all the internal ammo stores burn without exploding...