The reason is because of ffp. City and Chelsea didn't have that issue and were allowed to spend what they wanted initially which got them to where they are. When we have our new stadium we will be much better placed and by then hopefully they will have scrapped that pathetic ffp rule anyway and then you might appreciate the investment from Farhad and co.
Put it this way, if we didn't have the spending power he has put in and we had still gone through all this trial and error with new managers, then where do you think we would be now? I would bet in the championship for definite. We would probably have kept Martinez, been on a downward spiral after selling Lukaku and pretty much doing what Villa did and going down.
Its not Farhads fault all these managers have failed, most of them were accepted by the fanbase on appointment but the fans wanted out after the first signs of it going wrong. The only manager who did achieve his goals was allardyce and the fans hounded him out after going from relegation candidates to 8th. Is that Moshiris fault? I'm not sure how any blame can be attached to him for anything really.