The WTA have had 8 different semis finals for IW/Miami. Collins has come from the clouds to beat Venus easily. Venus seems to be the barometer for the tournament. She is always thereabouts but never a champion.
Feels a bit ew, but Isner has been a perennial Top 20 player for nearly a decade and had lost 3 Masters finals before. It's not like Zverev's form is any more reliable (3 Masters might have been premature for him as well).
Fine with the Isner win as a Career Masters. Isner makes these deep Masters runs out of the blue every year to stay in the top 20, so he might as well win one. Solid wins against Raonic, Del Potro, Zverev, etc. is a solid campaign. Winning at Miami (rather than something like Paris) is a fairly big achievement for him.