I know it sounds conspiratorial, but:
What's happening is an intentional shaking of this banking system. A stress test. To let go of weak hands that are not in line! To see if it's ok to go up a little bit more with the rate. Which he for sure will. Markets already know this and are moving ahead of with that expectation in mind.
The market for the most part sees this, and they've all moved in place in anticipation of the fed move.
If he wants to send the market scrambling again, then he will do anything but that
If he wants more stability of the markets, he'll do exactly that.
I don't think the banks would want another scramble and so they'll work together to minimize "beta" and so they'll all fall in line and do what's expected: 0.25 tomorrow, 100%
