can craniosacral therapy help babies sleep?

yes!

An infant's skull is soft, it is easily manipulated. This is what made it possible to pass through the birth canal. It takes about a year and a half to grow strong and solid.

I would be cautious about who you have work on your babies head during this fragile time.
Be sure they are well trained-in or have experience with doing Cranio-Sacral Therapy on Infants.

Ohh most definitely. Cranio modalities are a phenomenal way for increasing sleep quality.