Why only JUMBO 30 yr fixed rate goes up?

I think when Wells Fargo increased the rate from 6.875% to 8%, the main concern is that they THINK the long term interest rate will go up.

For the business perpective, compared to the ARM, 30 yr fixed rate program usually has lower return and higher risk for the banks.
For the Jumbo loans, the risks are even higher. So to protect
the banks themselves, they increased the rate a lot for the time being(which is not necessary at normal business environment). The rate may go lower in teh future when the turmoil settles.