There are a couple of potential reasons for a successful business to move. 1. landlord issues: Rent skyrockets, or landlord sells and wants the space, or renewing a lease becomes impossible. 2. Space issues. An old building might become uninhabitable or they must shut down temporarilly for major repairs and it wouldn't make business sense to be closed for that long.

But I do agree that a "second location" is much more likely. Also, they have a catering business, and the Malden space would have room to park catering trucks, it has a loading dock for food deliveries. I don't know anything about their catering facility, but it makes sense that if they have to cook food for catering, they might as well have a restaurant onsite for feeding it directly to people as well.