Ayn rand herself actually had a pretty good explanation of why this may be. She differentiated between a writer's technical skill and their "sense of life", and

Ayn rand herself actually had a pretty good explanation of why this may be. She differentiated between a writer's technical skill and their "sense of life", and said that one could appreciate a writer's skill but hate what their writing revealed about their unconscious attitudes about the universe, or conversely think a writer is trash but love what they have to say. I found the Fountainhead incredibly appealing when I first read it; you're right that it strikes a strong chord in people. But she breaks a lot of rules of what is by modern standards considered to be good writing. Her literary influences, though, were Victor Hugo and Ian Fleming (the James Bond author). So that's interesting company to keep. They both have that same vice, the love of the monologue. Fleming calls himself out on it in an essay that's been circling round lately.