I'm not sure if the 2x is supposed to be literal or not or just an illustration, but they note both were below expectations.
Kotaku UK said:Besides the technical problems with Windows 10, though, Lionhead’s bigger problem was that for the entirety of Fable Legends’ development cycle, the potential audience for the game was shrinking. Xbox One sales were falling far short of projections. Windows 10 installs, too, were nowhere near what Microsoft had planned. The scale just wasn’t there. And for a free-to-play game, scale is everything.
“Let’s be honest – we make our projections based on a series of assumptions,” reflects a former employee who worked closely with Microsoft. “There are supposed to be 2x as many Xboxes out there as there are right now. There are supposed to be 2x as many Windows 10 installs as there currently are. So now, when we look at how much money Legends could make in the free-to-play universe, you have to halve it. Because we can only reach half the audience that was projected.”
Source: http://www.kotaku.co.uk/2016/06/09/how-fable-legends-took-down-lionheadOne source reckons that the final decision was probably made about a week before, as Microsoft started doing its fiscal planning, deciding what products and studios to fund and not. Lionhead was not the only first-party studio that was having problems. Something had to give.
“I reckon [Phil Spencer] feels bad about Lionhead, but I think for him, he has to run all of Microsoft Studios as a business,” they say. “First-party studios isn’t doing so well. Halo 5 is a big miss, versus projections. Minecraft is a big miss, versus projections. Compared to either one of those, Lionhead is practically a rounding error. But I think if your division is under-performing, you have to go to your boss with something on the altar.”