The problem is, the club aren't trying to grow fanbase the same way the Blackhawks did. In a big sports city like Chicago, teams are trying to get people in the arena over the different sports teams. The fanbase grew because people from Chicago embraced the team due to the success.
Its different in London. If Chelsea are going through a particularly bad spell but Harlequins are winning the Rugby premiership every year, it doesn't mean that the people who would be going or supporting Chelsea, start following a different sport. Football is a lot more omnipresent here.Everyone follows a team .People from London and the surrounding area, the people who realistically make the core of the support (domestically at least), choose a team due to geographic proximity, family ties, or how often they go to the ground.
What I'm saying is that the "new" fans, are most likely from overseas. Whilst I'm sure that is great for the clubs finances, it does not then translate into more people coming to the ground every week , or travelling the country. Just because someone from Malaysia has fallen madly deeply in love with Chelsea, I don't think that is the same thing as growing a strong domestic fanbase, which ultimately sustains the club through more difficult times.
Basically the essential problem is that to often these days, people going to stamford bridge, even if they do genuinely care about Chelsea, are interested in getting a photo inside the the ground, buying everything in the Megastore, and taking photos throughout the game on their phone. They're not ingrained in the culture of what it actually means to be a Chelsea supporter, going every week, feeling the agony and the ecstasy.
In that way , its become more like an exchange. Come to Stamford Bridge , buy a shirt , watch the match, and suddenly your a "proper" Chelsea supporter. I'm sorry but its nowhere near the same thing, and I really think that unless the club can find a way of getting younger people in on a regular basis, then the we won't have many of our hardcore left.