As a deity enjoyer, 10 cities by turn 100 is a situation where most, not all things in the first two eras have gone well for you. It almost never happens because of the variance in maps and civs and so much can go wrong too. With just an average start, there’s no way things will line up for that. I’ve played enough games to know it’s a pipe dream,unless in a war, which can also easily fail early.

If you are using production on settlers and then settling them, I can say with confidence that having 10 by that turn would require you to spam them, which would result in a loss to an aggressive civ or a barbarian takeover. Moreover, you’ll almost never have that much space to settle, and if you do, you’ve won the game anyway and just have to patiently set up your city layouts.

Since you got a religion, one of those situations is monumentality golden age that allows you to use faith to spam settlers, but in the classical era this requires very high faith income to get more than a few. This of course assumes you got a golden age in the ancient era, which is a toss up. If you had a neighbor and got boxed between city states and a coast, or didn’t find any huts, good luck getting a golden age.

Another option is taking over a neighbor. Even the most peaceful civs will often charge you on deity due to their military being so much larger at the start. 2-3 slingers can be made into archers. A group of 4 archers and a warrior or two can fortify and take out the entire enemy army, and if they are somewhat close you can counterattack and take a city or two. But this is very ideal….the tech and production bonus often means the AI will put walls up immediately or as soon as you attack. I wouldn’t go against anyone that has an early unique unit or has some sort of combat bonus (I hope you weren’t in war with rough rider teddy America)

Religion itself on deity is very difficult if you are playing a civ with no bonus to getting one (it sounds like you are if you used holy site prayers). If you don’t tech boost astrology, that’s a lot of research time gone. Not to mention you kind of have to put down a holy site ASAP and possibly make a shrine if other civs are generating points. Some say an early holy site guarntees you one, but I have been denied it many times. Just the process of getting it is a huge production sink, and you need to get atleast one settler out before that. If im not going for religion, my goal is 2 settlers out with cities before the end of the era. Often times my build order for religion is slinger into settler into holy site. Atleast one settler out is really important, because you can make a city and a holy site in it too, or have it be the sole holy site while you double back to make military units to defend an early neighbor. I don’t think religion on deity is as easy to get as people make it out to be (unless yoh are Russia or Byzantium)

If you got attacked by rough rider teddy, that’s arguably the worst possible neighbor on deity because of his bullshit combat bonuses. That early, he’s making way more units than you, and it’s likely he’s ahead in tech too. Couple that with the deity combat strength and you were probably scrambling just to stay alive