Tiktok paid peanuts but had a large enough audience to get lots of attention. The money on Tiktok comes from brands being marketed (often via product placement), not necessarily from Tiktok itself. Tiktok does pay people, but not nearly as much as you'd think with how many influences are out there.

I don't think the existing product placement industry will suffer on alternatives, but Tiktok has what its competition lacks: an excellent algorithm, not bogged down by any ethics, optimised for pulling in as many people as possible. Filtering out ugly or disabled people and algorithmically censoring speech all across the spectrum would never pass on any open system, but it has worked wonders on Tiktok.

That's why I don't think open source alternatives will ever be popular, even if they find themselves backed by investors and paying out creators: they're still too ethical to be profitable.