The cycle of leaving and returning is endless and can go on as long as you comply. A narcissist gets bored very easily, and so it’s very hard for them to stay consistently loyal to a single person, so, they continue to move on from person to another and then in a circle again.

https://bornrealist.com/reasons-why-narcissists-often-go-after-the-same-partners-over-and-over-again/#:~:text=The%20cycle%20of%20leaving%20and%20returning%20is%20endless,to%20another%20and%20then%20in%20a%20circle%20again.