Fannie Mae and Freddie Mac

QUESTION: S&P downgraded Fannie Mae and Freddie Mac. Won't that cause mortgage rates to rise?
On Monday, the average interest rate on a 30-year, fixed-rate mortgage fell to 4.33%, according to Bankrate.com, down from 4.47% last week.

Fannie Mae and Freddie Mac

But homeowners with adjustable-rate mortgages might look at refinancing at a fixed rate, because interest rates could rise when the economy recovers. Q: If the S&P downgrade isn't driving up interest rates, why did markets fall so far Monday?

Fannie Mae and Freddie Mac

Standard & Poor’s has cut the triple A credit rating of government-backed mortgage financiers Fannie Mae and Freddie Mac following a similar downgrade of the US government.
Housing Crisis of 2007

Fannie Mae and Freddie Mac

In 1938, Fannie Mae was created to support FHA and create yet more home ownership opportunities.
If Not Fannie & Freddie, then what?
What about competitive interest rates?