Different collusion. And they didn’t say it was okay - just that they didn’t have any evidence that Trump himself had been involved.
Then the report went on to say as clearly as the justice department is allowed to say that Trump absolutely engaged in obstruction of justice. They couldn’t indict a sitting President, and you can’t make a public accusation against someone you aren’t going to indict.
Mueller said that if Trump were innocent of obstruction, he’d say he was, but that he would not say that. He laid out specific criteria for what constitutes obstruction, cited many specific occasions in which he met all those criteria, testified before Congress that if he weren’t the sitting President he would have brought charges against him, and said directly that it was Congress’s duty to impeach him.
But somehow the GOP convinced everyone that the Mueller report was an exonneration.