So the fans want a name director and a reliable franchise film. The director hired to make a reliable franchise film feels like since they're being advertised as a "name" they're valued for their creative input (okay so they're probably more savvy than that, but they at least hope they're valuable enough to have some real leverage). The studio knows that they need a "name" but that they also need to keep them in line so they make the kind of movie people expect.
> I wouldn't be surprised if for the next batch of Star Wars films they drop all pretence and just hire tv directors, like most of the Marvel films do now.
I've never watched the Harry Potter movies but it looks like they did the same thing halfway through the series.