See
System.String.Replace(String, String)[
^]. The first parameter is the old value (the string to be replaced), and the second one is the string to be inserted. You have passed these parameters interchanged.
Note also that you probably want to replace the comma instead (with optional trailing space). Otherwise you would also split strings containing spaces like "T2 Terminal International Airport" from your example.
So use
Replace(", ", System.Environment.NewLine)