I think the biggest reason is just the difference in exposure. Doom had a ton of pre-release because of Wolf3D but then had a buzz of its own. PC sales had also

I think the biggest reason is just the difference in exposure. Doom had a ton of pre-release because of Wolf3D but then had a buzz of its own. PC sales had also been steadily increasing so just in the time between the two games there were more PCs in consumer hands and pretty much all of them were capable of playing Doom. There were just more instances of Doom running than Wolf3D. Another aspect is Doom as an engine had longer legs. It got an official sequel not a year after its release as well as official "clones" in the form of Hexen. Hexen's own box advertised its relationship with Doom.