There are two ways to make a good D&D game: Either license the IP to a few companies (or just one) with proven track records of doing good work; or license it to anybody who wants it and let the best game win. The first option is preferable, but requires a top-quality studio willing to work on someone else's IP, and there aren't many of those. The ones who previously had relationships with WotC parted ways with them a while ago.
So they're left with the second option. The likely result will be a deluge of crap and a handful of gems. If WotC is smart, they will build relationships with the studios responsible for the gems, and thus transition to option #1.