No he wasn't, he granted himself that title. Then largely left on his own in ~2013 to focus on the (now discredited and defunct) "Bitcoin Foundation" that he created.
The people developing the Bitcoin project have been pretty stable since 2011.
There is this lovely time coded git-blame chart that was put up last year: https://bitcointalk.org/index.php?topic=1337008.0
People like Mike Hearn were always outsiders to the project, and have spent a lot of time doing this like arguing for blacklisting, blocking tor, and other things that most contributors think of as strongly at odds with the principles of the project.
He's still welcome to contribute (hundreds of people contribute to Core, only 3 of them has commit access), but it doesn't look like he's interested in that.