[blueash]

Slept in a Holiday Inn Express.... You admit that the damage to the neighbor's property was caused by the pool on your property. You admit that the existence of that damage was disclosed to you before you bought the home as you can see it in the sale's video.
When you buy a property you get both its assets [the land the building the landscaping] and the liabilities [you need to fix the landscaping if it violates our rules]

One of the liabilities that came with your property is the known damage it caused to your neighbor. You are responsible for it. You may have the option of going to your insurance carrier for protection, not sure if they have any here. You may have a better case against the pool installation company if they improperly installed the drainage system so that it drained in such a manner as to damage your neighbor's property.