Don't quite agree with Y Va as De Gea is a goalkeeper. His arrival won't have any impact on relative positions of any of the outfield players. The transfer fee won't be significant enough to force Madrid's hand to do any selling.
They've sacked all the good managers in top tier. Looks to me like they're treating Benitez as a glorified back up till the next managerial hot shot turns up. That is why they're not ready to invest in him contrary to their habit after seasons when did not win anything.
The only glaring hole in my theory is Klopp. Why didn't they go for Klopp? Does that mean they rate Benitez above him? Why are they not investing in Benitez then?