Yeah, but it's generally the kind of money that only allows having a mom-and-pop store. 1-2-5 employees, that's it. If you have a bigger initiative, you can't do it.
Instead, Mega Corp just buys you out when you burn out after many years of development, we see this happening regularly.
In general I think you are probably right. Many developer tools are small projects that can be developed by a single person, and it seems they often struggle to grow into to a bigger company. (I've experienced this struggle myself. For me, the problem was not lack of money)
On the other hand, I think Jetbrains shows that it is absolutely possible to build a huge company that sells nothing but developer tools.
There are also a bunch of mid-size companies that sell developer tools. I'm pretty sure there's more than 5 people at Navicat, Hex-Rays, or Panic, but I'm not sure how big these companies actually are.
Instead, Mega Corp just buys you out when you burn out after many years of development, we see this happening regularly.