Being ghosted after being asked availability to interview…

I’m a recent college grad and applying to jobs and I genuinely don’t understand the point of going back and forth emailing with someone who’s the head of their department (not HR) and them asking your availability to interview you and you send it over and they just ghost you after nothing… I thought I had made a really great impression and all of our emails were great but maybe they’re just super busy but it’s just so frustrating to feel left abandoned like that and no one telling you just plain out no