It would have been a waste of political capital to hold up an election he lost by 3 million votes. The concession was the right thing to do. There are people working to uncover all the irregularities and making sure all the votes get counted. In the unlikely event that there is something uncovered that changes things, he can always un-concede.

If he had been acting like a tin-foil hatted sore loser for the last few weeks, nobody would take his initiatives seriously. Now he can act with credibility.