I wondered whether he has a relegation clause that allows him to opt out joining if we were relegated so wouldn't join until we were mathematically safe. However if the Aab manager had already left then that is probably wide of the mark as Elfsborg couldn't then pull his contract.
As others have said, seems strange he wouldn't want to come in and try a few things in our final matches with the current squad to help decide who to retain and who to move on.