A strapping pin is a pin/IO that is used by the ESP32 during it’s boot up cycle to set certain modes. IO0 for instance is used to select if the ESP32 boots into download mode, or if it boots running your user code.
You are not allowed to alter it with a pullup/pulldown during boot, or it will not allow you to boot properly. You are only able to use that IO after your code is running.
For more information about strapping pins, please refer to the ESP32/ESP32-S2/ESP32-S3 datasheets on the Espressif website.