I just rewatched all Silva's fights with my gf and I don't believe prime Weidman could have beat a non-clowning Silva and I think Silva was on his way to a fairly easy win in the first fight but his ego and boredom with being champ got to him.
He was tired of being champ and was relieved to relinquish the title and Weidman was in the right place at the right time and he capitalized. And good on him. He wasn't winning that stand up and prior to Silva's silly antics he didn't seem like he was going to win that fight.
I'd have to put my money on Izzy, sorry. Weidman's a good guy, but I don't believe he was ever on either Silva's level or Izzy's. He got the gift and the curse from Anderson - beat him twice and then shit the bed as a career, including the freak curse of breaking his leg in the same way he broke Silva's. Right place, right time.
He made history and I'm happy for him, but he was never on Silva's level. No middleweight really ever was, to my mind, including Izzy.