He hasn't trained for months, and has gone MIA. He has declared he only wanted to join Atletico, so he don't care what bid Chelsea accepts he isn't going anywhere else. That gave all the advantages to Atleti. Guy is 29 as well compared to Lukaku who is 24 and has his best years ahead of him.
In normal scenario such a guy would see his price dropped terribly, yet Chelsea pretty much more than doubled their initial outlay on him.