Reraise to isolate?

[jaguar]

I watched this prima poker stream yesterday and one of the commentators was constantly talking of how the players didnt reraise enough to isolate from the button. I didnt understand anything of what he ment so can anyone please explain this play. I take a example hand from yesterdays broadcast.

6max game 25/50 all have at least 100BB stacks

All fold to cutoff who opens for 4BB with QTs
Button with KJs called

Commentator now starts telling that in this situation you have to decide if your hand is better or not and either fold or reraise to isolate. I simply dont understand what a reraise would gain you. Can someone elaborate.