What causes raids?

Is there an in-game explanation to the raid mechanics and how to possibly make them stop or calm down? I am on normal mode and get raided 3-5 times a year.

I’ve never seen raids 3-5 per year. I have seen raids once every 3-5 years though.

For me i have raid every year or every two years in normal mode…

as far as I know, raids are so frequent during excavations that raiders attack them, but they only go after 5 attackers and that several times

Excavations may cause a small-scale raid. If you excavate several relics in one year and unlucky enough, you will get raided four or five times a year. Therefore, you can consider sending soilders to guard your excavation sites next time.

I build a tower near my excavation site. and then move it when I excavate another.