the gods and goddesses should have realized that he is mortal thus whether by the sword or the slow passing of time he will still die thus their receiving tributes would end. Tondemo Skill ga Hontouni Tondemonai Iryoku wo Hakkishita Ken Nitsuite
idk if you found the answer but he kinda became immortal .. if i remember correctly it's because he received the chief god's smol blessing yeah ...
so i reread that part and in the ln it says that he got the small blessing of demiurge the 'big god' and he will live for like 1500 , like an long lived elf and that he's status changed from human to kind of human ... he also has can make elixir that can lengthen his life the full elixir ...