Do we need the backstory? It's space PCP for war. Jokes aside, look at how many times in war, we (and I mean a collective we because numerous countries have done this over the last century+) have given soldiers, pilots, etc amphetamines and more in order to improve their ability to fight, stay awake, and win the war.

M'Benga made a future drug that does all this which he prefers people don't use but keeps it just in case he has to save people or survive battles.

That's all the explanation I need. Old Trek didn't give us even that much most of the time - just treknobabble.