You know that Russia like to named each of its prototype with new name despite have commonality with existing stuff, named it Mi 8/17, Su-27/30/35/37, T-54/55, Mig 29/35 ?
If i can say radically, T-90 is bassically T-72B3 in steroid. It just add more optic, and add more ERA. (TBH, I hate ERA...