The Torah interjects to tell us that a baby boy has a bris on the eight day to tell us that it’s not just a technicality. There’s a build up to the momentous occasion.
When a person wants to be a Tzadik he gets an infinite amount of heavenly assistance. Thus, it’s easier to be a Tzaddik and receive that assistance than be a rasha and not get it at all.
Parshas Parah comes immediately following Purim to show us that it’s time to get ourselves ready for Pesach. Not just cleaning for chametz, but ourselves too.