Twitter isn’t dying. The users and content is still there. The people going to Mastodon are the niche group of techies. Mastodon isn’t for your casual or average twitter user.
I think news and ads ruined social media today. I do miss the days of MySpace and people used to log on , hangout and message each other. You used to to connect with your friends online. Today, social media isn’t really used like that anymore.