The variable $proc is defined outside of the loop. That’s why $proc.Count always stays the same inside the loop. And since you set $n in each loop iteration it actually never changes its value.
Regardless of that … it might be just an example and the original process you like to treat is something else but even a single Chrome window is assembled from more than one process. If you kill these processes you will pretty likely kill the functionality of Chrome or at least damage it severely.