Not in the slightest, tailwind even have their own UI library. Theirs is unstyled but there's nothing wrong with creating one with default styles.
Tailwind does not have their own UI library as reusable self-contained components. Instead Tailwind UI gives you the source code of these components so you can customize them to your needs. I much prefer that approach to that of pre-baked rigid components
I always thought that was so the Tailwind developers could generate revenue.
No, the components come with specific JS behaviours, and the documentation has the Tailwind classes you need to add separately (which means it's still modifiable if necessary).