Txurce
Deity
I wouldn't include luck, but I agree that you need an army regardless of your path to victory.
That's good, and should be obvious if it wasn't for how stupid vanilla's AI was.
I mean what would you do if a nearby civ was an easy target? Even as a cultural victory I'd probably war them, raze some cities and vassalize them. Otherwise you're leaving resources on the table.
When going tall, luck comes into play with runaways. War with them may not result in actual defeat, but just the unhappiness will set you back more than you can afford.
I often get greedy with easy targets, but have realized that friends and DPs are critical when going tall, and you don't want to develop a rep as a warmonger. Vassalizing is fine, but I've learned the cardinal rule is not to take a capital -- even when snagging a religion.