People are being harsh on Koeman. Both seasons he's had to have loads of players sold from under his nose. Liverpool especially keep pillaging them.
With financial backing he'd not only be able to keep making quality signings but also actually hold onto players (bar perhaps Rom and Stones). Also had some bad injury luck that exposed squad depth problems (Forster returning marked a big upturn in form).
Unfortunately he doesn't guarantee success like perhaps only Jose can, but he's done enough to suggest he could have us pushing for the top 4 at least.