Yeah, maybe embezzlement then, but still not theft.
Depends on what the exact relationship was - most companies go to amazing legal lengths to ensure that they disclaim any relationship between themselves and their contractors.
Which is not going to cut in their favor.
There have also been plenty of instances of folks much closer to having relationships + knowledge and not being found to be illegal (though rarely there has been civil liability). IE financial advisors exploiting inside knowledge of their clients portfolios + what their companies are up to to make trades that advantage their companies at the expense of their clients.
As for the rest - the intended net effect of almost all trades in finance is to cleverly transfer the value of everything you can to yourself ;). The only question is whether he had a relationship that makes that illegal or not.
