The thing is, they rarely sell the properties. At least from what I've seen. It's all unrealized appreciated value.
Most restaurants in Europe generate an average of 250k in net cash flow per average restaurant, that's few years of work before ROI.
McDonalds's Corp, the landlord, is in a better position but they also don't want to see stores fail, it's bad for their image.
Not that I think McDonald's will ever really find themselves in a pinch, but if they did, they would additionally be able to liquidate selected properties for cash. When you are rich enough, the promise of having money in the future is just as good as actually having money. It doesn't work like that for most of us, but that's the nature of risk assessment in finance.