Quote from Brad, taken from the comments section of his interview with Boogie2988:
"In a nutshell, our publisher was Microsoft and we had a deal with them to make a new AAA MMO.For about four years everything was going well and we were almost ready to start some early alpha testing of the game. Then there was a regime change at Microsoft, with the VP of their games devision leaving the company along with just about everyone who worked for him. The new group that was assigned to our project wasn't interested in doing an MMO. They accused us of being late and over budget. They wanted to push us out the door and launch the game one year early.
As was noted before,MS paid for this experiment for 4 years and the game wasn't even in alpha. You can argue regime change or discuss the fake tech demos, but at the end of the day they felt it was cheaper to let go of $30M than fund a game with no end in sight.
The game would not have even seen the light of day without SOE, which I still don't understand the reasoning behind. It probably would have been better for Brad if he had just shuttered Sigil as the game was terrible at release and remained a nasty pit of hitching and bugs for years afterwards.