Your credit score is just one of the things they look at when determining whether or not you qualify for a loan. Another big consideration is your debt to income ratio.
This is a bit of a ridiculous example, but it illustrates the point:
Let's say you make $10,000 per month, and your house payment is $9,000 per month. Now you apply for a car loan which has a monthly payment of $1,000 per month. You're going to get turned down, regardless of how good your credit is. Why? Because your total monthly debt service is equal to your total monthly income.
Once your monthly debt service exceeds a certain percentage of your monthly income, you won't get the loan, regardless of credit standing or the amount of the down payment you put down on the car.
I haven't looked into such things in many years, but your credit score would often affect the debt to income ratio "ceiling." The ceiling being the max debt to income ratio a lender would let you have and still qualify for the loan. People with bad credit would have a much lower debt to income ratio ceiling than those with good credit. And as I said, it has been years since I've looked at such things, and don't know if credit score is still used in determining max debt to income ratio.