Considering Chelsea's contract lengths, it's no wonder players chose them. No matter what happens - bad form, injuries - they're set for majority of their careers.

It also has the potential to massively backfire for Chelsea, we'll have to wait and see.

Because Chelsea's project is a lot more exciting, full of young talent, uber a manager that is known for developing talent, under an ownership that is willing to invest no matter what.

Additionally to the other replies, a lot of players (seemingly more prevelant in foreign players) have more of a desire to be in and around London given the choice.