Mr. Flynn sometimes seemed to be trying to achieve through business what he could not accomplish in government. He believed that the United States was engaged in a “world war” against Islamist militants, and that Washington’s national security elite had so thoroughly politicized the country’s intelligence agencies that few left in government could see the threat. The United States, he believed, needed to take a tougher line against the Islamic State, and it needed to cultivate Russia as an ally in the fight.
“He got out of the service and had a passion to reform the intelligence community, where he saw some deficiencies,” said Todd Wilcox, a former Green Beret and C.I.A. officer who founded Patriot Capital, a Florida-based defense contractor that named Mr. Flynn to an advisory board in 2015.
But Mr. Flynn also became entangled with controversial clients. One company that paid him, OSY Technologies, is part of a cyberweapons company whose software has been used to hack Mexican activists and an opposition leader in the Middle East. Another, a Boston company selling a technology to replace lie detectors, is accused by its former chief scientist of marketing a counterfeit version of his technology to foreign clients.
Dozens of interviews and a review of public documents suggest that Mr. Flynn’s business was as scattershot as it was ambitious — and that there were few opportunities he would pass up. His clients ranged from a drone manufacturer in Florida to major software companies; at one point, Mr. Flynn took a $5,000 gig as an expert witness in a personal injury case. Some of his clients came through a tight-knit circle of Iranian-Americans, one of whom became a key partner in Mr. Flynn’s businesses.