I had a similar experience recently with a well funded startup. There is no doubt that I can do the job well, as I helped with one of their engineers as a vendor. I corrected one of their components several times, when my contact there reached out to me for advice.

But my resume wasn't bulletproof (decent school, some job hopping) and I didn't express the requisite awe about their product or technical tasks (I gave my assessment that they have a good business plan but should expect modest growth, and the engineering tasks needed would be tedious to anyone honest). That's all I can think of, because I sure as hell didn't answer any questions incorrectly.

Also, for all my efforts, they ghosted on me afterwards.