"for loop" breaks after the "if statement" in it is True once

Question

1. def filter_list(list):
   for x in list:
       if isinstance(x, str) == True:
           list.remove(x)
       else:
           pass
   return list
   

input: [1, 2, "a", "b"]

output: [1, 2, 'b']

The for loop breaks after the "if statement" in it is true.