The Raspberry Pi Foundation was definitely optimizing for the IP their volunteers & employees were familiar with and had confidence in.
Other boards beat the Raspberry Pi in mainline kernel support, USB & Ethernet I/O & price years ago, but there is a significant ecosystem that the Foundation seeks to support, and the best way they know how to do so is with the tools they are intimately familiar with.
> Other boards beat the Raspberry Pi in mainline kernel support, USB & Ethernet I/O & price years ago
You sound knowledgeable, so I'll ask: if you don't care about the RPi ecosystem (or IoT use-cases at all, really), what's the optimum SBC across all those axes currently? Like, what board would you choose to base a cheap one-off HTPC+NAS on?
I like the OrangePi lineup, particularly the OrangePi PC Plus as it has 8GB eMMC and decent specs while being sub-$30 with a case and accessories: https://m.aliexpress.com/item/32668421022.html
For a NAS, nearly all of the OrangePis feature USB ports & ethernet that are directly wired to the SOC, so you aren't I/O limited like older Raspberry Pi's. That being said, the Allwinner H3 doesn't support 10 bit Hevc/H.265 acceleration, so you might want to go with a board based on a newer chip for a HTPC. Take a peek at LibreELEC, they have a decent HTPC distro for many SBCs.
Other boards beat the Raspberry Pi in mainline kernel support, USB & Ethernet I/O & price years ago, but there is a significant ecosystem that the Foundation seeks to support, and the best way they know how to do so is with the tools they are intimately familiar with.