Chelsea changed a lot after the British government forced Roman Arkadyevich Abramovich out of Chelsea as owner. Then Todd Boehly took over the club as the new owner which in the end made many changes on the management side. Todd Boehly was desperate to bring instant glory to Chelsea in his first season but the truth is that everything he's done this season hasn't turned out well.
In finance, they are still rich and spent lot of money for transfers in the last season. A biggest change in Chelsea is vision to develop the club which is not good under their current owner, Boehly. He does not have a good vision like Abramovich and it is harmful for Chelsea. Buying many players with very expensive cost like overpaid but they failed to buy players who match with their club tactics and current players they have.
Those new players failed to adapt to the club tactics and team-mates, it plus with bad choices for their coach position from Potter to Lampard, only makes thing worse.
I'm not entirely surprised how Chelsea have been this season because they are essentially in transition. It takes several seasons to build a good team and collaboration both internally and externally, and this will be achieved by Chelsea in the following seasons.
It changed a lot from winning Champions League with Tuchel, then sacking Tuchel and hiring Potter. They made many mistakes that all contributed to their bad performance in the past season. They must change it with Pochettino who is a better coach than Potter and Lampard. However, their transfer in this summer must be done better.