Well, if I judge this by what other publishers (Capcom and Ubisoft) have done, this is what I assume happened.
Speculation: Sometime after the announcement, EA decided that even if the multiplayer was quality, it wasn't going to be a major draw for the title. After analyzing the previous game's sales, I'm guessing that they noticed that the PC version of Dead Space didn't sell a whole ton relative to the console versions, so a manager in fear of the pirate boogeymen decided to delay the PC version of the game by 1-3 months in hopes that it would increase the sales of the console versions, as those are harder to pirate.
In reality, the sales change is very likely non-existent, but that doesn't seem to stop these people from making these annoying ass delays all the time.
But that's just my guess on the situation, judging by what I've seen happen quite a few times, most recently with the sudden delay of the PC version of Assassin's Creed 2, as well as the mysteriously disappearing PC version of Lost Planet 2.
I just really hope they bundle in all the DLC for free when it finally comes out, assuming I'm right. I'm generally much less annoyed when I get a bunch of extra stuff after waiting, like in the case of Red Faction: Guerrilla.