Car dealers do not normally make financing or leasing decisions on their own*. They normally use one of the various lenders that they have contacts with. The various lenders available may specialize in various types of buyers (e.g. good credit versus bad credit). Bad credit means a higher interest rate on a loan or money factor on a lease. Also, financing may have different credit criteria than leasing.
*A big semi-exception would be on a day when the lenders are closed (i.e. a weekend or holiday, when many people buy or lease cars), so the dealer will write a contract based on its assumption (from recent experience) of what it can get the buyer financed for, and then complete the loan with the lender on a business day. This is called a spot sale, and sometimes it goes wrong when the dealer’s assumption of financing is incorrect. Then the dealer will want the buyer to sign a new contract at a worse interest rate. More: http://www.edmunds.com/car-loan/dont-fall-prey-to-spot-delivery-scams-and-yo-yo-financing.html