In case you didn’t notice it, Barack Obama was unended by the backstage Biden team. He only endorsed Kamala Harris after all the other Democrat leaders did, as if he had wanted someone beside Harris to be the nominee. Eventually, he endorsed Harris, because he had no choice. Her team preempted him by choosing the nominee so quickly. It was a done deal.
The first reason he did not endorse Harris, was that he wanted Michelle Obama to be the nominee. That would keep him in power, as Michelle and he see political things in the same way. However, he was not in the loop of the backstage Biden team, which had the nomination of Harris sewn up, likely even before Biden withdrew. So, at that point, Obama was the loser.
The second setback, and, chronologically likely the first, also left him out. Though as much as the far-left communists act as a team, hardly ever fighting with each other publicly, there are rivalries. Whenever there is an acknowledged leader, those who are rivals for the same position tend to want him/her out. This happened with Yeltsin and Putin. It also happened with Andrew Cuomo and his Democrat rivals. Anyway, it happened with the Biden backstage team and Obama. Obama was the loser.
So, why is Obama back? Because those who “overthrew” him lost. Thus, Obama will be seen as the Democrat winner and re-assume his position as leader and influencer of the Democrat party.
Obama wins again.