Isn't that just because those are the hot topics du jour, and these grads happen to be one of the many groups pursuing these opportunities?

It's more a comment on the perception that HBS grads are behind the curve due to their unwillingness to innovate on their own, but perfectly willingness to enter (and exhaust) a field with parasitic behavior once it has proven to be fruitful.

A leading indicator of saturation, if you will.

They are trained to game systems. [Take tests, do better than peers, out think superiors, etc]. But they just need a path to follow. They will follow anything that makes the most money the fastest.