Not American, but my instinct is that the hype around this case is fundamentally different to Chauvin's and thus one shouldn't draw too many conclusions from what happened then.
Chauvin was never, ever going to get anything resembling a fair trial regardless of the facts around his case. BLM was a very close 2nd for international news story of the year in a year in which fucking covid happened. Here in the UK the BBC was reporting on the trial as if it were happening here. If Chauvin had have been found not guilty, there would have been mass protests in cities like London and Berlin, not just riots in the US. Maybe it's sad but the level of global interest in that case was such that there may have been a concern that if Chauvin weren't convicted then the international reputation of the US would decline.
Contrast with Rittenhouse, and the whole story has received very little attention outside of the US it seems. The only reason I know about it is from here and seeing people shitposting about it on 4chan. The BBC don't seem to be covering the trial in any major way. Even my American friends haven't mentioned it (and I have a couple mates who absolutely LOVE to politisperg, but don't seem interested in this one). The level of interest, and thus threat of retaliation if Rittenhouse is acquitted, is nowhere near as high. And I may be proven wrong on this very quickly, but I don't see any major riots happening even if he is fully acquitted. The protestors outside the court seem excessively spergy rather than being the types with balls to actually burn it down. Whereas if Chauvin had walked, it absolutely would have been the Summer of Sneed Pt. 2, instantaneously.