Trump fired Manafort and I don't think he cares for the man. He's kind of shady and wasn't forthcoming with Trump about ongoing legal issues, albeit issues that were probably made worse by deep state operatives turning up the heat so they could get headlines bad for Trump. Regardless, according to Cory Lewandowski Trump said in response to one such revelation in the press "I've got a crook running my campaign".
I suspect that if Trump is tempted at all to intervene, it's just because they are using Manafort to imply Trump is a Russian puppet, even though his case predates the campaign by years. And maybe because this whole imprisoned in solitary confinement without a trial is an injustice, plain and simple, which Trump seems to find offensive when he sees it. But that will be tempered by his apparant low opinion of Manafort as a person. I mean, an injustice is being done to Mike Flynn and Trump has no bad blood there yet he's not intervening. So in the aggregate, I would expect Manafort to look to his lawyers more than to a miracle from Trump.
IIRC, the Manafort case was one that Mueller couldn’t put away when he was FBI director. That he opened it up again is evidence of an animus toward Manafort on his part.
My sense is that Mueller wants all of Trump’s business financial records and that all of this is his building a case to get there.