I agree. I think what we're seeing is investment risk assessment as a proxy for a deep understanding in technology. After all, if you don't know how anything works, all you can do is look to what _has_ worked for you and other investors in the past.

I'm guessing here, but it's plausible that once a given stack has proven to make money, the fix is in. It wouldn't matter if it's the best choice out there or not. The track record itself makes it more attractive. Example: Ruby on Rails.