I bet your criteria for how to judge who the "top 10 best fighters" are is a whole lot looser and more subjective than how most websites do their rankings, no offense. Munoz was on a good roll, good enough roll to easily be top10 and arguably top5, at the time Weidman beat him.
And yes, a win over Okami would have been more impressive but it doesnt mean that Weidman rolling Munoz up like a pretzel for a whole round before knocking Munoz out in the 2nd was not hella impressive. You judge fighters an "actual ability" and Id say Weidman showed great fighting ability by toying and knocking out Munoz.