> This is a bit confusing to me because MySQL was released around the same time Postgres added SQL support but maybe it was because MySQL had a company behind it.

I think the main reason MySQL took off faster than Postgres originally is because it had better defaults. MySql worked out of the box on modern hardware. Postgres assumed you only have 4MB of memory until well into the 2010s, in part to make it keep running on everything it ever ran on in the past.

So when you first installed Postgres, it would perform terribly until you optimized it.

It's really a fantastic case study in setting good defaults.