It sounds like you’ve tried to make amends for your past immaturity and the misunderstandings as best you can, but these guys aren’t interested in forming deep connections with you. Maybe they can’t get past feelings of hurt and mistrust, but there’s nothing you can do to control that. You’ve matured and grown, and that will help you make new connections. I think your instinct to let that chapter close is correct. That doesn’t mean you have to fall out with them, definitely don’t do a big drama scene and flounce out of the WhatsApp group or anything, but let their treatment of you be a benchmark of how you treat them. These are people you can politely socialise with, so don’t burn any bridges, but they are not your “tribe”. This article by Mark Manson talks about romantic relationships, but the principles can be applied to friendships too.

https://markmanson.net/fuck-yes

Graduate studies are challenging, but also universities are great places to meet likeminded people. Maybe join (or set up) a board game society, or something similarly social, to practice your social skills and widen your circle. It takes time, but you’ll get there. Good luck.