Twitter's longtime CEO Ev Williams was pressured out of his job, his spin to the contrary notwithstanding, multiple sources have told Fortune, corroborating what we've been saying for nine months. But why?

"By October 2010, Williams had run out of steam," Fortune writes in its Twitter takedown about the company's "secret board meetings, executive power struggles" and "clipped wings." "Williams says he demoted himself ... Multiple sources close to the board say its members asked him to step aside, but no board member will confirm that."

There were some whispers that maybe Williams was being pushed out for drinking too much, which we could never get Williams to talk about. But the co-founder's personal behavior would in any case be a mere a side note among Twitter board members. His startup's overriding problem is much bigger than some conference boozing: It has developed no real business model, despite having raised $350 million in venture capital, most recently at a valuation of $3.7 billion. Fortune mentions that Twitter took in just $45 million in ad revenue last year, according to one estimate . That's a vanishingly small amount of money for a company taking as much investment as Twitter, even when you add in the $25 million Google and Microsoft are reportedly paying to index tweets in their respective search engines.

Twitter's long honeymoon period with the press appears to finally be ending. Fortune's story gave a nod to earlier press reports about how Twitter's U.S. traffic has plateaued and how many registered users end up quitting or barely using the service. The New York Times in October quoted former co-founder of Williams saying he "isn't CEO material" and highlighting other problems at Twitter. Even TechCrunch, which called our early coverage of Ev Williams' fall and Twitter's executive chaos "bullshit speculation," is finally acknowledging the company's turmoil and deep seated problems.

Ev Williams quit his titular post CEO job at Twitter last month, severing his day to day involvement with the company. But the reasons behind his ejection as boss of the company are still important. After all, if you figure out why the board hated Ev Williams' Twitter, you might actually be able to figure out where new CEO Dick Costolo's Twitter is heading. And right now that's far from clear.

[Photos of Williams via Getty Images]