To be fair I do think there is logic to his substitutions it's just that the logic isn't exciting or attacking. He started an attacking lineup which got us nowhere, bizarrely the defensive one somehow got the result.
He didn't try to make it more defensive, on the contrary. He wanted Fellaini further up the pitch but he didn't have any other midfielder left on the bench, so he put on Heitinga and took off the player who was the least likely to score.
You can criticise the fact that he sent out Barkley on loan when our bench is very short on midfielders but the sub itself made perfect sense from his point of view, even if it looked baffling to everyone else.