How this power control circuit works?
It is always a good idea to use transistor to control anything with any MCU as it minimizes the current that needs to be provided by MCU itself.
Here a small base current to T1 transistor (after MCU goes high on GPIO5) makes T1 conduct. So now there is a current path from +3.3V across R6 and R5 to ground. Which makes the GATE of FET1 also at ground turning it on. (actually voltage at gate is more than 0.3V if you account for R5-R6 voltage divider and 0.05-0.2V voltage drop from T1 Vce in saturation)
10k R6 is there to make sure that gate voltage goes back to +3.3V AFTER the T1 is turned off (not conducting) by MCU. FET1 could and would stay on if there is nothing to pull it HIGH.
So MCU goes LOW, T1 doesnt have base current anymore, it stops conducting. Now only current path is +3.3 to R6 to GATE of FET1. effectively GATE of FET1 is +3.3V