Why are bursts of high pressure air into the mouthpiece trumpet timed to coincide with moments when inside is already at its maximum?

Bursts of high pressure air into the mouthpiece of a trumpet are not usually timed to coincide with moments when the pressure inside is already at its maximum. Typically, the player's lips are used to create a buzzing sound by rapidly vibrating against the mouthpiece. This vibration creates alternating high and low pressure zones inside the mouthpiece, and the player uses their breath to control the timing and intensity of the air flow to produce the desired pitch and tone. The player's technique involves coordinating the air flow with the lip vibrations and the movements of the valves to produce the desired musical notes.