Anyone who pays attention to the web platform should know by now that any rationale Chrome (or Google in general) developers give for web platform decisions is

Anyone who pays attention to the web platform should know by now that any rationale Chrome (or Google in general) developers give for web platform decisions is made up. They repeatedly told us they had specific motives for AMP and it was all a lie, AMP was designed to tighten their grip on the advertising market. It's not the only example - the way their autoplay whitelist works is also transparently manipulative despite lies to the contrary - and I would bet money that MV3 is partially motivated by business incentives in the same way. Googlers' paychecks are signed by Ads and GCP and ad-blockers actively undermine the former.