But they did stick with it, AFAIK? They just took down their mastodon instance, that's absolutely not the same thing. Unless you mean to imply that all of us here, using this but not running our own instance, are also "not sticking it up for the Fediverse" or so.

Plus, let's not forget that by their underlying nature, Reddit and Twitter are not ad-driven via the ads shown directly. The real ads are in astroturfing, promotions and subtle pushing of products and ideas. And Lemmy, Mastodon, et al are just as susceptible to that, if not more so, lacking a usable central authority to curb such behavior if wanted.