Always assumed it was just momentum. They are beginner friendly.

If you need tutorials, a community, and some sort of support, you have to buy a Pi.

Maybe it is different now, but other SBCs just haven’t had those in the past. Raspberry Pis are unique in that sense.

You would think this would be the moment to disrupt the market, but I haven't seen much going on. I like my Orange Pi 5 though.