It's a fixer-upper that would require quite a bit of work on the inside.
There's your answer. They want cash offers only because they know most banks would never agree to finance the property in its current condition.
Think about how a mortgage works: the bank puts up their money now for you to buy a property. In turn, you promise to pay them back later. If you become unable to pay them back, the bank's only way to recoup the money they gave you is to sell the property through foreclosure. If they can't sell it for at least as much as your outstanding debt, they lose money.
So, when a buyer makes a purchase offer backed by a bank loan, an appraisal is usually required to complete the loan. An appraisal is conducted by a certified professional to confirm that the property's market value is actually worth what you're offering. This helps the bank understand what kind of risk they are assuming by lending you money.
Therefore, it becomes a risk calculation. Most banks aren't in the business of rehabbing homes, or even selling them at all. If a property is in rough shape, they won't finance it, because it would be too hard to recover losses in the event you default on the loan. If you're asking for a $300,000 loan on a property only worth $100,000, the risk is just too big. The bank won't give you a loan.
Real estate transactions can take a month or more. If a seller accepts a bank-financed offer, the property is off the market while the deal is in process. During that period, the seller is still responsible for all the expenses of the property - mortgage, taxes, utilities, etc. They also can't accept another offer. If the appraisal comes in too low, there's a good chance the whole transaction could fall through. If that happens, the seller has wasted time and money, and also has to start the whole process over again.
In very competitive markets, it's common for homes, even ones in uninhabitable condition, to sell for above market price. That's where the cash offers come in. With a cash offer, there's no appraisal and no bank. If both parties agree to the price, nothing more is required. So, a cash offer gives the seller assurance of a fast transaction.