I haven't seen (A)GPL done well and sucessfully in the (frontend) webdev space. I think some of the bigger component libraries are AGPL + commercial license, but they don't seem to have much in the way of community contributing, and would likely be just as successful if they were entirely closed.

If the commercial entity behind a dual-licensed project fails, will those that bought a commercial version contribute to its survival? Can they without licensing issues?

And preact seems simple enough that if there weren't X other JS frameworks, or if there is a specific niche only it fills, a lot of projects would try to clone it with a less restrictive license, probably win the mindshare race, and be the ones with a community that contributes, regardless of technical merit.

I might be wrong, I might be missing some shining counter-example, but I just don't see it happening in that space, as much as there are arguments why it would be in everybodies interest to make it succeed.