Bloomberg wouldn't serve in anyone's cabinet, especially not Trump's. They've had a good relationship in the past, but Bloomberg is very unimpressed by Trump's behavior and rhetoric.
No, Bloomberg was afraid Bernie Sanders would win. He dropped out as soon as Clinton took a significant delegate lead. He was always about stopping Sanders, not stopping Trump. The only thing he dislikes about Trump is that he might have lost to Sanders.
He's a pragmatist. He's always wanted to be president, but he doesn't want to deal with the BS of the two-party system. That's why he switched parties to run for mayor as a Republican. He saw an opportunity to run in the middle with Sanders/Trump, but he dropped out because Clinton would box him out. It had nothing to do with preference.
