Former president Joe Biden played an unwitting role in Donald Trump's breakup with Elon Musk.

The current president denounced the tech billionaire Thursday over his criticism of the Republican spending bill as a “disgusting abomination," but The Daily Beast reported a key turning point in their relationship involved an earlier social media post praising one of Biden's legislative triumphs.

“Abruptly ending the energy tax credits would threaten America’s energy independence and the reliability of our grid,” Tesla posted on the company's X account on May 28, and Musk reposted that to his 220 million followers, adding: “There is no change to tax incentives for oil & gas, just EV/solar."

Trump and his allies evidently felt betrayed by Musk's praise for the Biden-era initiative the president and other Republicans called the “green new scam."

“As the president said, he was very disappointed with Elon,” a White House source told the Daily Beast after the pair split.

The clean energy tax credits were approved as part of the Inflation Reduction Act, which Biden often boasted was "the largest climate investment in history," but Trump's sought-after bill would eliminate those credits and disqualify Tesla electric vehicles from a $7,500 incentive that JPMorgan estimated could cost Musk's company about $1.2 billion annually.

“I took away his EV Mandate that forced everyone to buy Electric Cars that nobody else wanted (that he knew for months I was going to do!), and he just went CRAZY!” posted Trump on Truth Social as their feud escalated.

While the tax credit isn't a mandate, as Trump claimed, the measure was signed into law by his greatest political rival.