Why didn't Dianne Feinstein ask Brett Kavanaugh about Christine Blasey Ford's accusations when she interviewed him?

So why did Dianne Feinstein did hold onto the letter for 6 weeks?

You can do your own research before spouting off. Ford requested that the information not be revealed but then she was outed by an unknown entity. But besides not involving yourself in the details you might consider how someone in Ford's position is treated when this kind of information, under these circumstances, is revealed.

Timing

Nothing about Ford's complaint is real.

Because she wants to delay Kavanaughs nominations. If she had brought it up 6 weeks ago we would have time to find out the truth. This is not about the truth. It's about delaying. Trust me. When this all falls down the Dims will have some thing else to use as an excuse to delay. They probably got one on the back burner. Made up a few weeks ago. Then they will bring it out at the eleventh hour.

Because at that time she did not have permission from the alleged victim to do so.