Broke up with my ex lost my closest friends, how do I rebuild?

Title pretty much sums it up to be honest. I left my partner of three years in early September, lost my friends that I met through him late Oktober. My relationship needed to end because my partner did a lot of not so nice things, the friends I met through him all encouraged me to end it. Then in October we both were invited to a party and my friends never even offered me a seat (i drove them there and then left again to get ice and he took „my“ spot) and I was mostly on my own for the whole party. I ended up texting my friends that this behaviour hurt me (specifically not asking if I wanted to join them) and it escalated into completely cutting off contact after I was accused of AI writing my apologies and some other stuff and the three friends basically ganging up on me. This is just to give you guys context. I used to talk to my ex and then these friends every day and now I‘ve realised I put all my eggs into one basket and while I have other friends it’s not the daily communication type. I don’t know how to rebuild from this. I feel so alone and isolated and I want to move on and I want to build more meaningful authentic connections and all that. But I just don’t know how. It feels like someone pulled the rug out from right under me and and I don’t even know where to start rebuilding now. I’m about 5-6 years younger than my former friends and 7 years younger than my ex and I feel like a 24 year old kid who got left at the bus stop. I‘d really like to know how other people coped with situations like this and what helped them rebuild their social circle. I pretty much abandoned my other friends during the relationship and while they don’t hold grudges I don’t know how to start reaching out and how I can cope better with spending time with myself. Not looking for validation or anything but maybe some life advice from someone who’s „been there done that“ would be nice. Disclaimer: I‘m in therapy as well and I have started getting better at texting my „og friendgroup“.