Why did Paimon possessing charlie?

Hi everyone, i’m out right now so i can’t just whack on the movie, so it could be mentioned and i just forgot

but i’ve been thinking about hereditary all day today and i was just thinking, if paimon wanted a male vessel, and was unsatisfied with charlie… then why did paimon bother with charlie, peter was already born, he’s the older sibling, why not get the grandma to help him possess peter… just skip the “middle man” of charlie

if it’s as simple as “it’s just fated to be this way” then why?