Swart says a number of clubs were interested in the Dutch midfielder prior to the coronavirus outbreak, including United's rivals Arsenal.
"There were six in total but because of the coronavirus it all ended. It was already a regular idea in March that he would go to Madrid, but because of the virus all of that was postponed. Clubs had no income and they could not sell players.
"Ultimately Manchester United pushed a move through and they are of course a great club. They used to be a championship club and they now want to build towards that again."