He was posting almost every day. Few posts daily and than disappeared. He didn't even say goodbye. He did not write that he was abandoning the project because BTC is ready enough for that. He just disappeared.
What exactly happened to Satoshi has not been clarified yet, although I believe that some of his close associates know much more than has ever been made public. It is possible that some additional information will be published over time, although it will be a distant history that will no longer be able to influence Bitcoin in any way.
If you read what actually happened behind the scenes in the early years, it can be clearly concluded that some individuals were not satisfied with the fact that Satoshi still makes all the important decisions. Apparently there was very strong pressure on Satoshi to actually leave, or at least leave most of the decisions to some other people - and from everything Satoshi did before his disappearance, it is clear that he did not leave until he made some important moves.
One of the best articles that describes in detail all the events and gives a very good insight into everything that happened between Satoshi and his close associates should be read by everyone. I will single out the following :
Still, it’s difficult to say if Satoshi’s decision to walk away was his alone. After all, over the year, there had been a dramatic change in tone toward his leadership.
As to whether he intended to leave, however, Satoshi was definite, his sign-off observable when he removed his name from Bitcoin’s copyright statements[X]. Thereafter, he would also update Bitcoin.org, adding the names and emails of other developers – including Andresen, Sirius, Laszlo and Nils Schneider (tcatm) – to its contact page and removing his own[X].
What little we know about the transition was represented by Andresen publicly when he claimed a week later to have received Satoshi’s “blessing” to start “more active project management.”[X]
In the interim, Andresen assumed the trappings of authority, putting out a “help wanted” post and making clear to new volunteers they would now need to move the project forward[X].
“Who is willing and able to help out? Don't ask permission, just jump in. Your reward will be recognition, admiration and respect. It is time to take Bitcoin from, essentially, a single programmer project to a robust open-source project with lots of contributors.”
