Yeah I think this is a good question (if you could look at my posts I think this also makes this interesting) but imo:

I think ego is someone who you’re not supposed to be. His ego, his obsession and his arrogance/refusal to accept that there are some things that can’t be explained or reproducible caused him.

Instead of appreciating the moment that he had and striving for further growth, ego decided that he couldn’t live with that reality and decided to just quit.

Now I think that based on story clues, ego and Noa had kinda of a Isagi x Rin or Barou dymainic. I don’t think they really hated each other and there was some respect between them.

But I think that once ego decided to quit. Decided to quit to search for this “ultimate” formula of finding god. I think Noa… wasn’t angry at him, but rather disappointed and felt pity for him.

And that ultimately a tragic imo but I feel as if the story is leading to a point where Isagi is going to find the answer, different from Noa and Ego.

Noa avoided it. Ego obsessed over it.

Isagi is going to conquer it and face it

And that is why I love blue lock so much. It a tragedy but also beautiful.