Don't mistake a small hyperbole for my argument, that's a strawman. The point is that Silva is absolutely the most picky/lazy counter-striker in MMA. He doesn't counter guys when he can't get them to over commit, or he can't find their rhythm. Weidman fought with a broken rhythm, and the only time he over committed he was in control of range so Silva couldn't counter anyway.
If Silva didn't clown as much, I assume it would have gone much like the second fight. A whole lot of nothing, him getting taken down, him trying to hit Weidman and failing except for leg kicks. Then again Weidman did look like he was getting tired, but he almost always fights with his mouth open so it's hard to tell and he clearly still had power at the end of the first fight.
Again, Silva clowns to get the best possible opportunities. Against someone who just wants to brawl like Forrest, that ensures that he's going to attack wildly. Against someone like Sonnen it's unnecessary, because Sonnen comes forward extremely hard. Even then, it's not like he did no clowning:
It's part of his game. He takes it to an extreme and gets emotional only when people won't engage with him consistently, like Maia or Weidman. And he looks pretty good leading, but he definitely couldn't just go and finish Maia whenever he wanted. It's not who he is as a fighter, and not his skill set. He just isn't elite moving forward like he is countering.
Weidman put a lot of things together that Silva hasn't faced. He was a strong wrestler who got an effortless take down early and landed several hard shots on the ground, hit Silva standing but didn't get hit, avoided all the clinch attempts, taunted back, fought with a broken rhythm, had solid and clever footwork and power in his hands. He wasn't desperate for a take down and he wasn't scared or desperate to engage, but had the skill to do both those things. Silva has never seen that before and the effect on him was obvious.