I think they are legit. Genesis Mining is a real company with great infrastructure; however their contract offers might fool customers. (again, this is normal in business - every party secures its own benefit)

Regarding AI, I believe software is much more important than hardware to develop an AI. Google leads the way as well as Amazon because they "own" the vast amount of data that is needed for the Machine Learning algorithms.

Everyday a new currency is getting created so, when BTC or ETH mining is over, I'm sure they'll find something to make use of the hardware. Plus, they will have earned their USD investment back for a few times until then ^^