Bitcoin price pumps and dips anytime of the day and not only overnight. I feel that your timezone is why you feel that it's always in the middle hours of the night. However, volatility is the nature of cryptocurrency and fundamental analysis and investors sentiment can come up anytime and thay will affect the market.
I don't think this is what the OP probably meant. This is a common expression in some countries.
"Overnight" means very quickly or suddenly, and it doesn't mean it only happens over night.Bingo. I think what we're dealing with here is an issue of English being a second language and a misunderstanding of a common English language idiom.
This misunderstanding is repeated throughout the thread by people who don't realize it has nothing to do with day or night.