What all went wrong with the Air India plane being flown by pilot high on weed?

The Air India Phuket-Delhi plane, flown by pilot who tested positive for marijuana, lost all three hydraulic systems at 4:02:44 pm and 4:02:45 pm on August 4, which caused a complete loss of elevators, ailerons and spoilers. At 04:02:46 pm, the autopilot disconnected and the co-pilot pitched the plane's nose fully-down. The hydraulic systems recovered within seconds after 04:02:51 pm.