Well, "win" as a noun is a word from Old English attested before 1150 [1].
And as a word firmly in the language it has its own specific uses in comparison to "victory". It would be silly or pompous to call a win in a sports game a "victory," for example. It would similarly be out of place to call a victory in a battle a win.
"Congrats *on the big win" doesn't sound out of place.
[1] https://www.oed.com/dictionary/win_n1?tab=factsheet#14538168