I agree you need significant amounts of resources / capital to do it. I disagree you need megacorps to do it. It's inefficient for the means of production to be held by a private company looking out for its own interests and wealth and not the good of society: even if you want the military to be more capable, the military-industrial complex is a bad way to do it. And the argument that startups need to spend money on their own fabs is an argument these shouldn't be in private, competitive hands.
At least the U.S. government does an absolutely terrible job with the capital-intensive infrastructure it touches. Having it be in charge of something like a nuclear reactor or a chip fab would end technological progress.
