He definitely had enough power, but as steve19 points, he could have estimated that such actions would have probably lowered his chances for reelection.
That's it. That is democracy. Unless he had 'an offer he could not refuse', he is guilty of a lot of betrayal (apart from crimes he can commit from a presidential position).
He is not there to do physics, he has been given power to explicitly do what cannot be done without power. Apologetic my ass.
If they did not want Obama in office, you would not even have seen his name anywhere on screen or in print.
Democracy in its true form has never existed in history as it is not really sustainable for many kinds of reasons, that all lead to disasters (people tend to vote for what is only good for them short-term leading to long-term losses, too many different groups arguing over X and Y and Z leading to stand-stills, etc).
I'm not saying we have it good right now, but it was for a while (last 150 years). But nothing lasts forever and eventually all systems decline and collapse.
Out of how many candidates were you selecting? 300 million? Or just a few, with long political careers? You don't get to the point of being an actually electable candidate if you could stir up a real mess within the establishment.
Candidates can and almost all do take an unlimited amount of money from private donors to fund their campaigns, likely in exchange for favourable legislation. Obama gathered $1072.6m like this in 2012. Obama owes his donors big time I would say.
https://www.washingtonpost.com/blogs/plum-line/wp/2013/04/30...
If it was truly hidden from him... then who is to say he has the power to stop it?
Assuming he could get his party behind him.