I see lots of people claiming this "is bad" for "Mastodon" and I don't get it. I think it's great. The main need in society right now is to get people off Xitter - regardless of whether it's to Threads, Bluesky or Mastodon.
All these services are/will be interoperable to more or less extent, which means those of us who want to be in control of our data and presence can select to be here on Mastodon. Others have other needs and values - and that's fine.
That a commercial actor benefiting financially from attracting new users do so is very different to the Fediverse, which for all intents and purposes attracting more users is a financial loss for whomever is operating the service atm.