Newbie trying to analyze transformer driver circuit.

Dec 2019
West of Chuchutanal Point
Hello, folks. I am rather new to electrical engineering, but am eager to learn. Right now, I am having trouble understanding the purpose of all the components in the circuit image attached.

The purpose of this circuit is to pulse the primary coil of a transformer with a variable frequency pulse, denoted by "Gated Pulse," which will be externally controlled, at a 5V high and 0V low. The primary coil is powered by 50V 3A and is pulsed by opening and closing the NPN transistor labeled 'NTE2365.'

I am having trouble understanding what all the other transistors are intended to do. It appears that the part of the circuit in the red selection is intended to assure that the pulse is exactly 5V high, in case the supply signal is not consistent. The problem is that it seems to me that if you would remove everything in the red and green selections, and connect the gated pulse directly to the base of the last PNP transistor, you would have the same outcome. Also, I do not know why the voltage to the gates is 2.5V as a low, instead of 0V.

If you have any insight on this, please show me where I steered wrong.