Tailwind is a direct response to how the "C" in "CSS" actually sucks, so there's no surprise that it's so popular.

The "C" (Cascade) in CSS doesn't suck, the education about it sucks.

People don't know how it works, then things go wrong so they learn to work around it.

That's what led to things like div + class soup that you get with the BEM naming convention or Tailwind.

The cascade is actually awesome, super powerful and if you know how to use it, it can greatly simplify your code.

Education is the problem and the solution.

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To anyone outside the CSS space, this is the closest analogy I can find:

In the American education system, there was a recent-ish change where children are "taught" to read using a method of just learning the shape of every word (e.g. "thermally" has a th at the start and ly at the end, so it must be the word "thermally", despite other similar looking words like thematically).

The method was disproven but the American education system still uses it.

Now illiteracy rates are climbing where almost 1/4 Americans (USA) can't read.

It's basically the same thing with CSS, where developers don't know what the code they're reading/writing is actually going to do.