Sanders, after being stabbed by the Party, bowed to the Party supporting Clinton. Not the Chinese Party, the US Democratic Party…if there is much difference.
Punts aside, it shows like in America (and mostly everywhere) candidates are party puppets for the good and the bad.
Even Trump is, at the end, a Republican Party.
The US has three branches, President, Congress and the Supreme Court to avoid any “coup” temptation (unless you describe a shadow coup the power of the American lobbies).
But the damage has been done. Lots if Sanders voters will vote the Green Presidential candidate Jill Stein, De facto empowering Trump.