Bloomberg article from several months back talking about ZeniMax being sold & mentioning they've been considering selling Zenimax/Bethesda for several years:
From Banking Scandal to Video-Game CEO to Billion-Dollar Score
Video-game trade shows aren’t known for dispensing high-end whisky, but there it was at the Bethesda Softworks exhibit: $100 bottles of Glenmorangie, flowing freely.
www.bloomberg.com
But much like in Hollywood, franchises such as Fallout and Elder Scrolls remain valuable, as consumers continue to play them online and purchase updates and items within the games. As industry valuations rose, Altman considered selling ZeniMax for several years and at one point was close to a deal with rival Electronic Arts Inc.
In the end, he found the perfect choice: a classy operator at a fancy price.