I'm told that in addition to Ivanka Trump, the presidential confidants making a last-minute pitch to soften the Paris deal included national security adviser H.R. McMaster, who argued to President Trump that he could accomplish what he needed to domestically, while adding significant caveats that would avoid alienating allies.
Trump rejected the advice in part because he thought a clean exit looked stronger, and partly because he was tired of all the conflicting advice he was getting.
But the biggest reason was all about that base: Using the muscle memory from the campaign, Trump is increasingly obsessed with his core voters. Officials explain that Trump and his inner circle learned in the darkest days of the campaign that they could power through by doubling down and focusing on the the base, so they're bringing those instincts to government.