Why did the mayans settle were they did? what resources made them settle there?

I think there's a pretty good argument that the Mayans built cities in places that had a spiritual power or meaning to them at least some of the time. They didn't always build cities in the available locations with the best/most resources.

If you look at a place like Uxmal in the Yucatan, there is no available water source yet though an impressively large effort they built a system of rain water collection and storage to meet their needs.

In other cities wet lands were turned into agriculturally productive areas buy building systems of canals and elevated fields.

Tulum, is the best example I know of a city site that makes sense to us. It's on the ocean, a trade route. It corresponds to a gap in the reef allowing for access and some protection from bad weather. It's on a cliff making it easier to defend. It has a fresh water cenote. Other city sites it's not always obvious why they selected them.

For the most part however, I would say a water source is pretty key. With the noted exception of Uxmal and other sights near Uxmal like Kabah. Most other sites I've been too have an obvious water source like a river or a cenote.

Where Did The Mayans Settle