These guys came in with zero BJJ experience while the BJJ had been doing stand-up for a long time. Nowadays all the info is out in the open so a few months of BJJ experience will nullify an expert if it is with punches elbows knees kicks.
I think the pendulum is swinging back to grappling because look at how the Dagistanis dominate strikers and grapplers alike. I dont think Dana White likes grappling so he keeps giving contracts to strikers or fighters know that knockouts get bonuses. I don't think he ever wanted khabib to be as successful as he was because he knows knock outs sell ppv. Then it turned out people liked how he smeshed on ground so it worked out okay.
So you got a lot of weak black belts out there...even makhachev said they need to start taking away some black belts when he submitted Olivierra.