RPis get sold more to the businesses and startups that started with them in 2010s, rather than hobbyists now.

If you cannot negotiate a good deal with the big industrial silicon manufacturers but you want good up-to-date kernels, RPis are a perfect option.

There are SoMs or SBCs with other CPUs like NXP or MediaTek that has more or less mainline support. However, they ask more money. The kernel contributions are also a bit on the shakier side which requires spending expensive developer time to deal with kernel issues that the CPU and the board manufacturer missed.

Raspberry Pi’s keep selling because the software ecosystem is solid.

Yeah they do keep selling, I wonder though if hobbyist sales have dropped.