Rejected after 5 rounds of interviews, but they are still actively looking for someone for the role

Hi everybody! I assume this type of post isn't anything new, but I wanted to write to maybe get other people's perspective.

During summer, I applied to a junior position in one company. It's a good company and I felt I checked all the boxes, and it's a job in a field that doesn't have many such opportunities. I went through five rounds of interviews and a technical interview, and was told to expect decision by Monday after the last one. Well, sure enough, on Friday before that Monday I saw that the Linkedin add for the job had been reposted after my last interview, so I knew that rejection was probably coming my way. I still hoped, but Monday passed and I didn't hear from them, but on Wednesday the rejection mail did finally come. I'm mentioning this delay in their decision because up to that point they would always inform me about the next round on time, and in the rejection mail she did acknowledge that they "took some additional time to align internally", but I don't know if that's an HR code for something or if I'm reading too much into it. I was disappointed and, since she did even offer to "jump on a call" if I have any more questions, I did send a follow-up mail asking for any specific feedback. She replied saying they chose someone else who had more experience in one aspect because they needed someone who could step into that part of the job quickly. So, you know, I thought better luck next time.

However, they never took the job down from their web-site, and few weeks ago they reposted the job add on the Linkedin and they even made several social media posts promoting the position. One of the people working there is coming to my college to give a lecture about that field of work (and probably to promote the position) and my professor sent us notification about that, so this is actually what prompted me to post this.

I assume that they actually didn't hire anyone back then. I just can't understand why they couldn't tell me the real reason why they didn't hire me. I really gave my all during those long five rounds and I at least expected some honesty, especially since they did seem sincere during the time I was in interviewing process. And the rejection email ended up with words along the lines "we’d love to stay in touch for any future opportunities", so I don't understand why they would take so much time to write a rather long rejection mail if they didn't like me that much, because they did seem to encourage me to reapply in the future. Perhaps it's a generic message that they send out to anyone, but I don't think so because it was rather personal and long and unlike to other rejection mails I've received, so I'm really confused.

So, why am I writing exactly? Perhaps just to ask why do you think they rejected me. Do you think they really had someone and it fell through, or what do you think could have been so offputting with me to reject me after five rounds if they still can't find anyone? Because I guess that's what hurts the most, the thought of that final interview being so awful, that they decided that nobody is better than me. And all for a junior position... I really thought they could at least give me a try.

I guess I was also thinking of reaching out again, but I don't know what I would ask. It's not that I want them to hire me, but I would just like to understand what happened, since I did put so much time and effort into those interviews.

Sorry for a really long post, every answer and suggestion is appreciated

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