No, he didn't. If Comey was fired any earlier, then the allegations of obstruction of justice would have had more credibility.
It's no coincidence that Trump waited until AFTER Comey had said in his public testimony before the U.S. Senate in early May that President Trump was not the subject of an FBI investigation.
That was the trigger that allowed Trump to fire him. Once this point was made clear in sworn testimony by the FBI director, then firing the FBI director (by definition) could not legally be considered an act of obstruction of justice.
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