Apple was going under in the 90s. Then Microsoft bailed them out to avoid anti-trust problems.
That's not entirely accurate...
Apple did have a fair amount of cash on their books in the 90s (that was part of what inspired the famous Michael Dell quote about shutting down the company and giving the cash back to the shareholders). Microsoft's "bail-out," though, was more about press than about money. $150 million wasn't that much.
You're right that Apple was going under in the 90s. Why? Because everybody said so. And if you're dealing with a company that's going under, do you really want to float them credit? As I understand it, even Motorola was basically making them pay cash for CPUs. Nobody wanted to be left holding the bag.
That makes it difficult to operate.
Apple didn't necessarily need money--again, they had quite a bit. What they needed was a vote of confidence. The agreement with Microsoft provided that vote of confidence that Apple wasn't going to go out of business.