The revelation this week that Carl Icahn has been helping President-elect Donald Trump choose cabinet nominees might help explain why JPMorgan chief Jamie Dimon is not going to Washington.

Trump on Thursday named billionaire shareholder activist Icahn as his special adviser on regulatory reform.

Icahn liked Treasury pick Steven Mnuchin, and did not favor Dimon, who desired the job, according to a source close to the situation.

Dimon’s people kept telling the media he did not want the position, but the sources said that was not the case.

Neither Trump nor Icahn uses any of the large bulge-bracket Wall Street banks to fund their deals. Trump usually works with Deutsche, and Icahn deals with Jefferies.

Icahn supports the Volcker Rule, which stops banks from making certain kinds of risky investments, and is wary of the big banks, sources said.

In “Danger Ahead,” his September 2015 self-produced video about the economy and how Trump could help America, Icahn said, “Teddy Roosevelt was great — he stood up to J.P. Morgan.”

So might have Icahn.

A JPMorgan spokesman directed On the Money to a Thursday statement in which Dimon said, “I don’t think I’m suited to be Secretary of the Treasury. I love what I do. I’m not ready to do something else.”

Trump this month named Dimon as part of his 16-member President’s Strategic and Policy Forum group that will give him perspectives of business leaders.