#1 Roman Abramovich's
The club has seen a massive change in fortunes since it was acquired by Roman Abramovich, whose deep pockets played a large part in making Chelsea's transformation possible. The Russian oligarch pumped large amounts of his own money to the club and invested heavily in the infrastructure of the club. While this has helped the club no end, it has also led to the attribution of Chelsea's success with the financial clout of their owner.
Fans of other clubs have called out Chelsea for 'buying success' for several years now. Transfers like that of Arjen Robben have provoked the ire of aforementioned fans because they came during a time when clubs focused on bringing forth talented footballers from their own academies.
Another aspect of Roman Abramovich's spending has been that the club began administering itself like a business. A revolving door policy was put in place which meant that managers who did not meet expectations would be promptly fired and replaced.
This would eventually become the way that all clubs handled their business, but in the years of good old Sir Alex Ferguson, it seemed ludicrous to think that the manager's job was as fleeting as Chelsea made it out to be.