We've given all four managers more time than they deserved. Each and every one of them was a sunken ship long before we actually sacked them. Moyes and LvG should've been gone by Christmas in those seasons, Ole should've been gone by September/October and Mourinho should have been gone the moment he started falling out with everyone. We have been incredibly patient, no other big club would've given those managers the time of day we have.
Ole has had more than enough time to imprint some sort of style of play, to improve results, to show what he's capable of, and has, quite frankly, failed on every front.
plus, a top-class manager earns the right to more time based on what they have achieved previously and their record of building great sides when given time to do so. You think if we hired someone as good as Klopp that we should expect him to immediately chase titles and sack him without letting him build a team? Don't be so ridiculous.