The Asura God Clan and Evure God Clan stayed at the opposite extremes of their star system, slowly conquering territories at the edges of Shen Ze.
They had significant authority in the middle areas, but couldn't be called as overlords due to the presence of Qing Mei Sect and many other powerhouses.
The Evure God Clan had a ton of experts, all at Legendary Ranking, but they couldn't become the overlords at the center as everyone would band together and attack them. The chances of them winning weren't low, but the losses weren't worth the trouble.
Likewise, if the Asura God Clan tried to take control of the center, the Evure God Clan would ally with the central forces and attack them. This could lead to them getting totally wiped out, so they never took such a meaningless risk either.