Well, NowGamer has an interview in which Trent Oster suggested that the negative fan reaction to Mass Effect 3 and Star Wars: The Old Republic were things that pushed Ray and Greg into leaving the gaming industry.

Ex-BioWare co-founder and Baldur's Gate developer, Trent Oster, believes the negative fan reaction to Mass Effect 3 and Star Wars: The Old Republic could have attributed to Ray Muzyka and Greg Zeschuk's decision to leave BioWare and the games industry.
Speaking to NowGamer, Oster explained that on his last meeting with Zeschuk, the developer was visibly exhausted.

"The last time I met up with [Greg], I felt his exhaustion," explained Oster. "Punch out, eject, get the hell out", was my suggestions to him and it hit closer to the mark than I had realised. I also think the Mass Effect 3 fan reaction and the Old Republic fans negativity was just too much."

"You have to love games and you put your heart into them to create them. To have the fans creating petitions against the work is pretty hard to take, especially when you've spent the last few years crunching overtime to try and ship a game. It can be hard to shut off the overwhelming negativity the internet spews forth, especially when it has your name or the name of your company in it."

Though Oster wasn't surprised when Zeschuk announced his retirement from the industry, when Muzyka did the same it did come as a shock.

"Ray surprised me," explained Oster. "I had him pegged as an EA lifer. My thought was the Ray agenda was to first usurp Frank Gibeau and then later John Riccotello as CEO."

"I'm sure the internal culture at EA had pinned the Old Republic conversion to free to play as a failure and hung that completely on Ray, so that would have hurt his upward climb. But, I figured he would fight harder. EA upper management must have been even worse than I thought."

Fan Negativity Was Too Much for Bioware Owners