How about the fact that Broadcom essentially enabled the Pi to be created in the first place?

Broadcom "enabled" the Pi to be created because the SoC for the original RPi 1 was a flop. They wanted to use it for Set Top Box (Cable TV, Google TV etc) devices but couldn't find any buyers

One of the engineers who worked on it worked out a deal with Broadcom to simply reuse the design and market it toward education instead

And it boots with the GPU which is not 3D accelerated in version 4 because the whole project was done by one person who just left. This is one of most popular SBCs out there. I wish it was a bit better.

Are there any high performance single-board computers on the market currently? I use a lot of Rpi's in personal projects, and I've been thinking about a home file server in a super small form-factor. What I would like is an SBC somewhere on the size scale of a smartphone, with performance in the range of a current flagship phone.

Does something like this exist?

This is exactly what I want too. What comes close is the Pine64 Pro.

Broadcom is neither the first nor only company making SoCs. The RPi people just happened to have someone working there.

Nobody said any of those things. The Rpi is good. Broadcom makes it.