Just because I'm curious as to the answers this might generate, who would cheer for them?
My take.....
I suppose they would attract "new" fans but so many of the younger generation (14-25), the part of a fan base that supports the long term health of a franchise, are HUGE Cavs. They were really galvanized to their team during the LeBron era and that would seemingly cut out a massive portion of potential supporters.
Do you really just start cheering for another team because they're closer? Or what is ultimately your motivation for latching on to a new NBA team? When another one is 140 miles away? I think that's the huge piece people undersell.
I'm sure this is where everyone starts discussing the Reds / Indians or the Browns / Bengals but those teams were founded / formed in the pre modern era of sports television / the internet. You were almost forced in to watching / supporting the closer team because local radio and TV broadcasts were all you had at your disposal. That dynamic just does not exist any more and I think it is why some expansion teams struggle, long term, with keeping a fan base.
Comparing how close teams are, that came in to existence 30 years ago, is a pointless exercise in my opinion. It just doesn't apply to how a modern team will be accepted and what kind of success they can expect to have (based on geographic ties). For $20 a month I can keep watching the team I already cheer for, in HD, on my couch. Converting the post internet fan to a new franchise, when a team is already even remotely close, is MUCH harder than converting a pre internet fan. There's more games, more highlights, more box scores, more messages boards, etc. etc. at their disposal. They can keep up with their team SOOOOO much easier that simply putting a franchise a few miles closer is, in many (if not most) cases, not going to matter.
There will always be an initial "new car smell" for a team / franchise but once they stop winning (if they ever start), they don't have any history to fall back on. The reason I love the Cavs (and any sports team for that matter) is because of the tangible memories I have associated with the team. I'm emotionally invested in them. Remove the memories or start from scratch and most people just don't have the same level of dedication (tickets, merchandise, etc.) or nearly the amount of patience. Further complicate things by putting the franchise too close to another one, in the same state and it could be a disaster.