I don’t think it replaced bootstrap either, but I think it’s sort of the Jquery problem.

Jquery was handling element selection, manipulation, behaviors, futures/promises, ajax calls etc.

Somebody came along in each of those categories and “specialized” such that jquery was left as the bloated old choice.

Bootstrap was awesome, but as component based libraries like react/vue etc came around, I don’t need component level css helpers as much.

And then tailwind helped fill in the gap of being quite a bit more explicit and granular.