No, that's not really why. It is because nobody else has their _ecosystem_; they have a lot of soft lock-in.
This isn’t just an nvidia thing. Why was Intel so dominant for decades? Largely not due to secret magic technology, but due to _ecosystem_. A PPC601 was substantially faster than a pentium, but of little use to you if your whole ecosystem was x86, say. Now nvidia’s ecosystem advantage isn’t as strong as Intel’s was, but it’s not nothing, either.
(Eventually, even Intel itself was unable to deal with this; Itanium failed miserably, largely due not to external competition but due to competition with the x86, though it did have other issues.)
It’s also notable that nvidia’s adventures in markets where someone _else_ has the ecosystem advantage have been less successful. In particular, see their attempts to break into mobile chip land; realistically, it was easier for most OEMs just to use Qualcomm.