I have Linux (OpenWRT) running on a router with 64MB RAM and 16MB of flash storage. And it works flawlessy. Also have Linux on a second WiFi router, my TV (LG WebOS), one phone, a laptop and a computer. (And I forgot about the Raspberry Pi and the VPS.)
Meh. You're right... However... Most things will run either Doom or Linux (or both). And nobody cares whether they have been designed to do it, or not. 🐧
Intel Atom was already almost nothing when they were first released. They struggled to even run the OS they came with, so much that Windows "Starter" edition was made where you could only run a certain number of programs at once.
A single core Pentium 4 from the previous generation would have probably stomped all the Atoms.