I apologize if I made it seem like I was blaming the victim; I was genuinely interested in learning how one would know the reason they were rejected. I've often been rejected and wondered why.

I don't at all find it hard to believe some interviewers would be biased against older candidates, especially for junior roles. However, given the person who posted seemed to have such a wealth of knowledge and experience, I was very surprised that they wouldn't have a very easy time finding a job even if places that refuse to hire older workers exist.