AlphaBay is now behind DreamMarket. And DM will not implement XMR they stated. In their Forum also no one asks for that. I did some research and AB once claimed they did it cause their customers demand it. I looked through the whole board but I couldn't find any demand for that. Somehow I think the group who said AB just used this opportunity to pump and dump is probably right.
For all you know Dream Market is right now "scrubbing" a bunch of BTC by suppressing the price and accumulating Monero for a big announcement coming soon! If it were me, and I was as crooked as these people... it would be a no brainer after watching the last rise to an ATH.
Edit: In fact I would be surprised if there weren't a lot of others doing the same thing!