Little while ago in my current game a lot of people switched to Buddhism, quite a few were already following some other religion when their entire civ - or most of it - magically had Buddhism added to it and the spread popped up to 50% of the world's following over a single turn.
I later found out this was because barbarian-spawned Isabella managed to build the Bible wonder
(Still think it's a tad strong, even with the reduced effectiveness it was given)
Needless to say, this boosted my income a great deal as my super-merchant city doubling as the Taoist and Buddhism Holy City
(The former having been buried after one of only two practitioners swapped out of it due to Isabella's wonder) allowing me to continue running Republic even at 29 cities, several off-continent, and inflating my Mastery Score even further. Speaking of which, that's at 173 with my 2nd place rival being at 33.
Short of some miracle on the AI's part (Or some World Building assistance on mine), I think it's safe to say this game is won by now. I know Mastery means a lot of surprises can happen at the end of the game, and with Permanent Alliances enabled maybe some of the AI will team up and then pose a threat later, but for the time being I'm refusing to build any more wonders and am keeping war declarations and such to a mininum. Gifting techs and etc where I can without upsetting my friends, since I don't want this game getting all boring since I'm nearing the Modern era - I don't get to see that often!