Bob's Deli has a number of on-going costs, like the lease for their storefront, contracts with suppliers to deliver goods, maybe a business loan from a local bank that got them going in the first place.
These are all liabilities that you, the new buyer, must take on. You can't just rule from on high and say these business deals were with the old Bob's Deli and go away with the purchase. An example of a purchaser (apparently/allegedly) trying to say that former liabilities no longer apply: Disney buying up Fox, or Lucasfilm, and saying they no longer have to pay royalties out to authors who wrote novelizations of films, or expanded universe properties[1]
[1]https://www.theverge.com/2020/11/19/21578621/disney-alan-dea...
https://arstechnica.com/tech-policy/2023/01/twitters-landlor...
https://www.nytimes.com/2023/02/03/technology/twitter-elon-m...
It does nothing else, the building is worth $100m and the loan amount is $95m.
So the company is worth $5m (the difference) and you could buy it for about that much (ignore whatever the company might DO with the building).
But now the real estate market crashed, the building could only be sold for $80m, but the loan is still $95m. Now the company is worth -$15m. So you could buy it for a dollar, but you still have a building worth less than the loan on it.
E.g. Saudi National Bank, who announced no more cash to CS