Proves that a team of rag-tag fighters can cripple a technologically superior force. Viva la revolucion!
Seriously though, amazing ain't it?
ISIS also have Abram tanks, humvees and anti tank weapons they got from American Base in Mosul. The only explanation why the ISIS destroyed the Iraqi tanks it is because they ambushed it.
The problem is that while still being m1a1 tanks they lack armor and another few features :
The United States supplied 140 refurbished M1A1 Abrams tanks to Iraq between 2010 and 2012. While they have new equipment to improve situational awareness, they do not have the depleted uranium amour package that increases protection over the tank's frontal arc