Every fighter needs to know BJJ, but it isn't or hasn't been the dominant art for a long time, though it's still necessary
Judo gets scoffed at by many and it isn't obviously the preferred grappling art, that's a mix of wrestling and bjj
However, having expertise in Judo is the icing on the cake and many experienced fighters struggle to defend against it when up against the cage
Khabib/Islam are a new breed of grappler and can mix their style perfectly with striking
Some idiot last night (can't remember who) dared Islam to fight Gordon Ryan in mma? Lol
A 200 plus pound Islam would destroy Gordon in mma, or the street easily