I'm new to the boards, and I'm certainly not well-versed in the history of franchises that went dark, like the RiverKings. But I can throw out some conjecture on all this conjecture.
The buyer (be it Sir Charles, Sir Elton John, or the late Charles Bronson) is just buying the franchise rights, I imagine. The buyer wouldn't buy the company that owned the RiverKings, what with all its debt. But the old owner can sell the franchise rights as an asset. After doing so, with the only substantial asset the company owned sold, the RiverKings would likely declare bankruptcy and close their books.
Why buy a suspended franchise instead of a sparkling new expansion team? It could come down to simple cost. I have no idea what the going price is from the league for an expansion franchise, to be fair. But with the recent addition of a solid market in QC, and all the talk of expansion that's beginning to bounce around, sometimes leagues get a little ahead of themselves and overprice new franchises.
On the flip side, if the RiverKings aren't going to return to their former arena, be it because of the Hustle, old debt, or whatever, then the organization has nothing but franchise rights. The brand, fan base, etc., are all lost for a team that will restart in a new market. So stripped down, the balance sheet is the rights to a franchise, old debt, and not much else. So the RiverKings can unload their only real asset and close their books.
Expansion can put the league and franchise owners at odds if it's executed poorly, especially when there are franchises that are struggling or which have gone dark, like the RiverKings. If the league is selling expansion while the team is looking for a buyer, then the league and team are essentially competition. It could result in a good deal for the buyer, and some uncomfortable situations for the league. I remember in the old af2, the league would actively sell expansions franchises every chance it got. At the same time, struggling organizations were given a concrete deadline to commit for the next season, even if they were actively looking to sell. Instead of the league serving as a broker, matching willing buyers with eager sellers, it became competition for the struggling teams. The result was embarrassing turnover and awkward league meetings.
Again, I'm just throwing around a few ideas from the outside looking in. I could be way off. But I wouldn't get too caught up in the RiverKings' old debt, because that's not following the new team.