Don't expect Cook or any others out there to move this out of "Lean R" because in their view, Vance is the "weakest" candidate of all. What is attractive to Republicans and right-leaning independents is now antithetical to what professional class liberal pundits view as a "strong candidate" so naturally, they are going to massively underestimate just how Republican Ohio has become.
There's a better case to be made for Oz being a weak candidate, because he actually does have a substantial portion of the R base disliking him, and it's unclear if that'll heal before November.
I feel like a lot of "experts" in the media will claim the Republican nominee will be the weakest no matter who it is. Trump could have endorsed Jane Timken and a lot of people would say that she was the worst candidate despite it clearly being Mandel.