I think one of the reasons people now believe that Cain was the end of prime JDS, was the Ubereem loss.
When Alistair was on a roll, KOing everyone in kickboxing and MMA, the consensus on Sherdog was that the only heavyweight in the UFC that would beat him 10 times out of 10 was Junior Dos Santos.
"JDS is waaay too technical a striker, and he's a big and strong guy, Ubereem won't be able to bully him against the cage, he wouldn't be able to submit him, plus AO has a weak chin and JDS' boxing is as crisp as they come at HW, he would KTFO of Overeem in MMA, he's simply a nightmare match-up for him."
So when they fought (holy shit, already 6 years ago??) and Overeem ran through Junior, that belief was shattered and most fans never really looked at JDS the same way IMHO
Seriously, read some old threads about this match-up, it's like today with, let's say N'Gannou/Gane vs Jon Jones.
The consensus is that both these guys would beat Jones, and that N'Gannou in particular is a nightmare match-up and would knock him out 9 times out of 10.
And for Ubereem/JDS, that was a belief that lasted for years, that he was
the guy to stop AO in his tracks.