> I never understood how to capitalize headlines correctly. Can someone eli5 ?:D

On HN, copy/paste is usually a safe bet (with a few exceptions): https://news.ycombinator.com/newsguidelines.html

If you mean in general, Wikipedia sums it up pretty well: https://en.wikipedia.org/wiki/Title_case

Like a big chunk of the language, English capitalisation is nonsensical and descriptivist. Different organisations have different rules just like different audiences have different expectations, and there is no single way to capitalise words in titles.

I'm with the parent comment on this one: for this particular headline it makes sense to lowercase "teams", since the HN audience will tend to correlate the uppercase version with the incorrect meaning of the headline.

Generally, capitalize longer words. But this really depends on the style book you choose to follow (MLA, APA, CMOS). See: https://en.wikipedia.org/wiki/Title_case

In English, the most common convention is to capitalize every word, or every word except small ones like articles and prepositions (the, of, for).

See also this nice title-case converter web app: https://titlecaseconverter.com/