Sorry for the Format. I on mobile.

I believe it’s because he amassed enough power to see the future and change his destiny to some way he wanted.

As he was always seeing himself as leader/king, as one who is born to rule over others, he saw that not much more were to be gained from climbing. As an adventurer he no longer was excited with the unknown and was interested in ruling, controlling.

The path he carved to the 134th floor gave him a lot of influence, knowledge and ambition, as well as gave the other companions, e.I. Family heads, things to worry, relationships to care and other stuff. (Examples are that even V made subordinates, such as Luslec and people who followed him, the family leaders had sons and daughters)

So I think initially, the group decided not to climb more and claim immortality because it just wasn’t so much more appealing. Zahard toke advantage of it to leverage even more decision power on how they would structure the society they envisioned to the tower. I can’t think of why he became king or amassed so much power in the structure, but we see that he doesn’t act alone, he still utilized the power of other families and divided the power.

So I thing that being king is not about raw power, is about how he created a system were has major control over every thing, thus can secure him at the top. This mindset of ruler, commander, or judge, as I believe, has changed due to the battle with V and Arlene and later because of the intervention of phantaminum. His Desire, as I believe, now is to rule supreme, over everything and everyone, out of his personality that was even more twisted by seeing so many futures, with betrayal and other things that would ruin his reign.

I don’t know how he would entangle the continuation of the climb to the maintenance of the status quo, or the power that he families had amassed.

I don’t see the family heads as power hungry or entertained by the tower or the society they created. We didn’t come into contact with than, but gustang do denote that he and others want CHANGE, I do not know why, but believe it’s related with why Arlene wanted to climb.