I wouldn't even blame Lampard for anything aas he came late to the party and then was asked to fix what couldn't be fixed within just a couple of weeks. Fundamental mistakes have been made and there are really better jobs out there then fixing a plethora of problems within a club in a short period of time, but I can understand that Lampard went for it. He saw an opportunity for himself and was hoping to turn it around and perhaps get a chance for a long-term contract. Most people would have done the same and I wouldn't say it was a mistake to hire him temporarily. But the damage was done before. Now they are off to a fresh restart, but their way back up is a long one.
Agree, Frank Lampard is never been blamed as what happen to Chelsea in this last season with he joined when ship was already drowned if we can blame anyone its owner which done few big mistakes just by his own and have result like this which is surely shocking for the fans but here I also agreed instead of hiring him as temporary if they talk about long term contract then surely we can expect better result from him but its another mistake from new management of the Chelsea which create big mess-up, and now they are looking for the new start of next season with new coach and many changes which are surely important before start and having good situation for them to start with positive mindset.
Lampard may not be the reason why they weren't bad, but he is certainly not a big help neither and I am expecting him not to be that great neither. This is why it is quite important to realize that he is not going to be helping them all that much neither, that's not how it works at all.
I personally believe that he is going to cause the team to be about the same as this season so they are going to sack him and get someone else. He was just the interim and he is not going to be staying for much longer. However, if by some miracle he stays and he is the manager for next season, I bet that they are not going to do that much better, not saying they will worse, they may do a little bit better, but not all that much, they need to be a lot better than what they did this season and Lampard can't make that happen.