1. To be fair the with rate for town hovered around 70% for most of its history and that was without a written strategy.
2. The point payout was even for the entire setups history as it was blacklisted the moment the point payout changed.
3. Honestly that is a big understatement especially that dice roll. A sniper hipfiring at start is a 1d4 roll which turns to a 1d3 when Gallis outs, Not shooting D1 turns the shot into 1d2 but means the Snoop has a 1d5 chance to spot your gun. At the same time the Politician's alignment is a soft variable that is hard to account for at any given moment.
This is just the tip but as you can see there are far more "decision factors" then you say.
Maybe the setup is just too much to take in for a 5 man game without a very well written strategy. For example it wasn't uncommon for players to not understand why the Gallis should out D1 and be lynched or why there was a Snoop in the setup.
Players not knowing how to play the setup only accounted for so much though. Newbs, trolls, mutes, and short attention spans are what Sniper winrate got dragged down like in Prayers game:
https://epicmafia.com/game/4555728