Magi

Hi I just finished sinbad manga and the anime of labyrinth of magic so I have the basic knowledge of the series and I don’t mind any spoilers Firstly why does sinbad not just kill the magi judaar? Why does yunan not help sinbad more as we see other magi’s helping their candidates more Also considering how sinbad started the ending was pretty bad and disappointing we didn’t see him conquer any of the other dungeon nor did we see him have any good training arch or any other side charecter development after the first few arch’s Why was suddenly sinbad so weak at the end when he has the ability to destroy countries. Also why didn’t he train himself to be strong without the vessels We also didn’t see the full powers of his djinns. Overall the manga could be better. What are your opinions on this?