If they've already bought coins, they probably had a lot to do with the runup from $100 to $1000. It's less of a big deal.
In the long run I think the latter is the bigger deal, because it would mean interest from credible mainstream investors. That could entice others to enter the market as well.
True. The big deal here isn't that fortress is buying coins. Its that the consumer public will be accessing bitcoin in significantly larger quantities.