How was Lucas in control of the previous home-video releases if he didn't control the rights?
I'm not certain of the legal minutia, but I think FOX just has exclusive distribution rights on the OT, and not rights over the specific content of the releases. Basically, any time Lucasfilm wanted to put out a new version of the OT, FOX alone got to distribute the films, but they didn't have any control of what version of the films Lucas wanted to release.
And yes, I still think it is nonsensical for the original unaltered trilogy to not be available in a proper release. There is clearly a demand for the films in their original forms as evidenced from various sources (originaltrilogy.org, The People vs. George Lucas documentary, a widespread bootleg market for HD copies of the original films, and so on). And I don't really buy the whole "artistic vision" argument because Lucas changed his vision with every single release of the films after 1997 (remember when Luke screamed "Neveeeeer!" when falling down the Cloud City shaft at the end of Empire? It was in the theatrical re-release and the SE VHS release, but removed from later releases.) And some of the changes he made in later versions were just so minute and baffling, (blinking Ewoks, R2 hiding behind even more rocks from the Jawas, etc).
Eventually, I just came to chalk it up to a neurotic need he apparently had to make little changes here and there with every possible release just because of 1) the possibilities of changing technology and trying to keep the films looking current with the latest tech, 2) the old adage that art is never completed and merely abandoned (and Lucas found himself in a position where he never really was forced to abandon it), 3) trying to offer something new with each release, and 4) perhaps even as a passive-aggressive jab at the fans who complained about the changes.