Why doesn’t the circuit with self resetting overvoltage protector immediately power on?

This situation is very normal. The overvoltage protector will only be powered on after it detects that the voltage is normal and stable. For example, the JGgq-80/1P+N type overvoltage and undervoltage protector launched by Wenzhou Jiangguang Electric Technology Co., Ltd. can be powered on when the voltage is detected to be normal and stable, and can trip off when the overvoltage is 275V and the undervoltage is 170V, effectively protecting the circuit and equipment