Signal's SMS support was basically just a novelty in most of the world. Where there really isn't much chance of Signal taking over any time soon.
There is virtually no benefit for the average user to use Signal over Whatsapp, unlike the possible benefits of Signal over SMS/iMessage. Telegram on the other hand is very attractive to them because of all the bells and whistles it has. The only difference Signal has from Whatsapp is that there's next to no one using it, and given how a lot of the world runs on low end phones, having an app on your phone to chat only with like 1 person at best is a waste of space.
Signal axing SMS support got it into an awkward spot where it doesn't have "anything" going for it in neither its home country or everywhere else.
I guess in theory yes, because sponsors would eventually notice a drop in people spending money through the creator.
Personally, I haven't and won't ever use a product just because my favourite entertainer was paid to say its good. Before SponsorBlock I just manually skipped or tuned them out anyway, so I never counted in the first place.