A google scholar search for "amd security" turns up less than 100k results while a search for "intel security" has <2 million results.

I dont think it has much to do with competence, the order of complexity in these chips are reaching super human levels of intellect to decipher. Finding vulnerabilities is hard but safeguarding against them is even harder. Take 'spectre' for instance, it is a fundamental problem with the speculative architecture can't really get rid of it.