If a person says they want to see Mastodon scale to support 100 million users, a lot of Mastodon users will jump on that person's neck. ??♂️ They'll be accused of having "VC brain", or being obsessed with hyper growth.
It's not about hyper growth for growth's sake. If you truly believe that Twitter is bad(tm) and Mastodon is good(tm), and that people should leave Twitter, then where exactly do you think those people should go? There's hundreds of millions of them.