Rock and a hard place. They were 7ish years from their last elder scrolls release, and knew they had at least 7 (probably) for the next one. Their poor planning caused it, but the fans were so loud that they had to do something.

And what an underwhelming something. Studio could have started work on ES6 shortly after Skyrim and had another amazing game out by now, but dawdled. They were at their peak, they could have doubled the number of teams and pumped out fallout and es every other year. But they wasted their opportunity.