This is the *key* thing people don't understand about social media adoption.
Companies like Twitter / Facebook / SnapChat have *vast* teams of sales people. They offer support in setting up accounts, priority support lines, branding and moderation expertise.
Individuals mostly don't see that. So it appears that your local council just decided one day to join Twitter. They didn't - they were sold a product.
Mastodon's growth is (mostly) organic - and that has a limit.