Prosecutors established that Menendez used his office to promote the personal and financial interests of Salomon Melgen, a wealthy Florida eye doctor. He asked the State Department to intervene in Melgen's favor in a port dispute with the Dominican Republic. He also helped secure visas for a few of Melgen's girlfriends.
Prosecutors also established that Melgen provided lavish vacations, flights on a private jet and $600,000 in political contributions to Menendez. The story of the underaged hookers involved was left out of the trial.
The jury accepted these facts, but was unable to reach a verdict, saying that prosecutors failed to prove the first point was a direct result of the second point. In their mind, NJ Senator Menendez was just doing the bidding of a Florida businessman because he's a nice guy. And the Florida businessman was flying Menendez around on his jet and giving him hundreds of thousands of dollars because Bob is so likeable. The trial ended with a hung jury.
A month later Melgen was sentenced to 17 years in prison for Medicare fraud.
You forgot two key details, which caused him to be prosecuted over other corrupt Democrats:
He opposed the Iran deal.
He opposed the opening to Cuba.