Mastadon, is just a leftwing version of Parler.
Not trying to be political, but a spade is a spade. For years we have had all these poor excuses of alternate social medias that people threatened to go to from one political leaning, only to either never go, or to go and return to Twitter or FB a short time later. This is just the opposite political leaning version of that.
It is very similar to saying if your candidate doesn't win you will move out of the country, and yet no one actually ever leaves.
What a lot of people find out is they are used to having a lot of followers and interaction that was built over time on Twitter, FB etc. And when they go to these new alternates, it is very new, with very few people, and in the days of expected instant gratification, they dont like the fact that they have 1/100th or much less than that of the following that they had on the previous platform, and they soon fall back to those. This is especially true for people that make their living from the popularity contest that is Social media marketing.
Whether you are right or left leaning, going to these alternates has never really worked out as people expected. They just dont gain the instant users fast enough, and even if they did, it would likely be that their systems have not been built to handle that kind of mass increase all at once and they would run into mass technical failures, and people would be discouraged by the influx of technical bugs.
Maybe this one will be different than the dozens of other alternate platforms out there already that are mostly stagnant, but I doubt it.