How can he immediately try to forget me?

We were together 2 years and we initially broke up a couple weeks ago but I needed time to think before saying it was final and we chatted a little bit here and there. I finally made it official on Tuesday, saying that he deserves someone that doesn’t question the future together all the time. The breakup came from me not really seeing a future with him because he doesn’t take his future seriously and doesn’t really care about himself. He said he saw where I was coming from and felt like he failed me and that he would do everything to make things right… so during the 2 weeks that I was thinking, he said he was already making progress on himself, which made me feel guilty for forcing his hand and also hesitant that it’s true change because it’s not coming from him. I had asked for a month of space but he reached out to me every other day which made it really difficult hence why we didn’t wait a full month. When things were official (I thought, at least) that it was very amicable and ending as if the future wasn’t set in stone for us and maybe we’d have a chance at at LEAST being friends… but 2 days later my friend texts me screenshots of him on tinder… He’s on there saying he’s looking for a “long term relationship” and is using selfies from inside MY apartment. I’ve been so hurt by this. He doesn’t know that I know and everyone says to be the bigger person and just act like this all never happened and focus on myself… but how can I? I’m so upset that he gets to push all these sad feelings down and just talk to new people rather than actually feeling the grief. It’s really hard not to feel like the last 2 years were nothing when he immediately runs to strangers for distraction/validation… We had SUCH a lovely relationship the only issue is he wouldn’t really try to grow up. We talked about the future all the time and marriage… it was just hard to picture it fully all the time when he wouldn’t take certain things seriously. How the fuck can anyone just act like none of this happened? It was 2 years of my life and I thought it was beautiful and not over but now it’s over over and I don’t know what to do with this rage and disappointment. I keep blaming myself, but if this is how he’s going to react then I likely had good reason for my feelings and it’s probably good that I ended things since this just proves he doesn’t want to do any sort of reflection or work on the relationship or himself. Idk what to do.