Unless it was just urban legend, VHS supposedly won out over Betamax because there was more porn available. It was the first “killer app” and helped make early rental stores profitable.

That was just urban legend I'm pretty sure. The reason it was able to be made profitable by video rental stores, I believe, is because JVC was more willing to license out their technology than Sony, so it was cheaper and more available to the average consumer. VHS also came out with more/had more recording styles more faster, and was more willing to degrade the integrity of their system, and degrade video quality, compared to Sony.

I forget if this was the case to begin with, or if this was a retroactive codec/recording style, but you could watch a full home theater VHS copy of a movie with one VHS tape, compared to the two betamax tapes you would need. That contributes, on top of not being a more proprietary technology, to a cheaper overall price. You could also, at a certain point, record multiple hours of a basketball game, in really shitty quality, if you wanted.

Basically, VHS benefited from a sort of economy of scale, and you were able to record more for less money total, which was rapidly becoming more appealing and more relevant, compared to the marginal quality gains of betamax, as things like VCRs and more accessible home movies started to hit the home video market.

I think the only major hits betamax ended up having was sort of filling out a gap in more mid-quality video recordings for stuff like TV shows, on the production end, because they were of higher quality than VHS, but I don't remember much about that.