Why would your credit score affect the interest amount?

the interest amount is a set number that cannot change.
the companies are required to charge more interest to people with higher numbers.
better credit makes you more reliable in paying off a loan, so you get a lower interest rate.
better credit means you have more money, so you get charged the higher percentage, similar to graduated income tax.

Better credit makes you more reliable in paying off a loan, so you get a lower interest rate.

Explanation:

The higher your credit score, the lower the interest rate it will be as well as the longer period you will have to pay off the loan, for you are "trusted" that you will be able to pay it off within the set time. However, if your credit score is terrible, it usually means that you spend more than you make, which makes it hard for you to get a loan for you are deemed as a "reckless" spender who cannot be trusted to repay on time.

~

always include the steps and/or background required to get to the final answer. let’s other people understand and solve future problems on their own.