The cap hit is largely irrelevant to a cap floor team like Anaheim and teams in a similar situation, with the cap rising they may actually find it preferable to have a player with a higher cap hit than his actual salary. A non-cap-constrained team isn't looking at him like an 8m cap hit, they're looking at him as a 6m dman ... which these days isn't exorbitant, and the term isn't crazy.
If they move Fowler (who has a lower cap hit but higher actual salary), they end up raising their cap total to keep up with the rising floor, while reducing the money spent. They can also now move Fowler AND Dumoulin yet still have two veterans under contract for next year (Gudas and Trouba) to go with all those young dmen, instead of having to go shopping for one in the offseason. They weren't gonna go into next year with Gudas and five young dmen.