I wonder if Fediverse, Blue Sky, etc will catch, or if it'll end up in the same boat. Threads too (yes it's backed by Meta, but G+ had Google behind it ...)
1. Meta's entire business is social apps, and Google's is not. There are strategic differences in approach as a result. 2. Google+ was an attempt to disrupt Facebook's rise at the height of Facebook's popularity. People _liked_ FB then - so trying to get them to switch to another product was harder. Threads shipped during a time of volatility with Xitter and is poised to capture more of that audience as Xitter continues to decay.
In terms of how things will change in the space over time, Threads choice to support ActivityPub will probably mean good things for the Fediverse in general, at least in the short term (3E notwithstanding), and could ultimately serve to be the arbiter that kills BlueSky and the AT Protocol.