I think two things made it red. The first is the referee's position, which made it obvious to see that Wilson didn't move towards the ball and rather targeted the player. From a different angle that might not have been as obvious. The second is the time of the game and the score, whilst not right I suspect if that happened in the first half he would have gone yellow. At the end of the game with the score meaning the game is over as a contest, the safest option there is to go red as it prevents any possible retribution. Players really don't like it when one of their team mates is hacked down like that, so getting the offender off the pitch is probably the best approach.