Trump's negotiation skills are probably overrated.
It's pretty easy to negotiate from a position of strength where there's an imbalance of power. But in a checks and balance system, it's a different ball game. Trump's ultimatum probably lost him as many votes as it got him. Most people don't like being pushed around.
His negotiating skills are plainly overrated. He bragged that he was going to cut a great deal with pharma, including negotiating lower prices on medications. He met with pharma leaders and they ate his lunch.
He has a record of cutting terrible deals. He overpaid for the Plaza Hotel, spent way to much on it, then his creditors took it from him and had to sell it for a loss. He couldn't negotiate traditional loans for his casinos, so he borrowed through junk bonds at 14%, guaranteeing that they'd fail from day one. His negotiating skills are simply one more thing he's bragged about until gullible people believed him. They certainly haven't been in evidence during his presidency.
I think the 'make-or-break' vote demand was a political gambit. It put an end to an episode that was highlighting his incompetence day after day. He was trying to separate himself, with an insouciant manner that implied, "Hey, this is their deal--do it or don't." The fact that it went down in flames didn't matter to him, because he never had any real concern over anyone's insurance in the first place.