In this case probably because we want to remain on good terms with Dortmund by holding off on completing the transfer until they secure a good deal for the replacement. Think about it, we will likely have to negotiate with them again in the near future for one or both of Haaland and Bellingham (although I believe the former has a release clause that kicks in a couple of windows from now).This won’t get done until Dortmund have got their replacement lined up - don’t think it will be Depay as Lyon normally try and screw everyone over and it would be obvious to them if they came in for him now that they had a bounty of cash - unless a deal in principal has been agreed and it won’t be announced until after they are out of the CL?
However, just seems that everything has to be such a long drawn out saga with very Utd transfer - why can’t we be fast and assertive and just get things done?