Ego of the Celestials was a conscious planet, capable of devouring other planets to increase his own power.
He was somewhat similar to Galactus in that regard, though far weaker.
Rimuru was not particularly interested in Ego. Instead, the Extraordinary team attacking Ego grew noticeably wary upon spotting Rimuru's group's spaceship, even briefly easing up on the already overwhelmed Ego.
This alone showed that, within Extraordinary Space, what all Extraordinary people feared and treated most cautiously were clearly their own kind.
Considering that they might become his employees, Rimuru did not deliberately provoke them. After stating that they were merely passing through in search of Thanos and asking about Thanos's whereabouts, he left the area.
Even after discovering that the other side had only one demigod, and that his own group could easily crush them in combat, he did not make a move to steal Ego, their prey.
Because Rimuru did not want to appear overly domineering.
In a campaign world, the cost of killing a demigod was enormous. Even the penalty for killing a Sequence 5 was considerable. That was why Yinyin Qingcao had immediately concluded that Zhi Ge would not kill them after she decisively surrendered.
So even if they were far stronger than Ego, Rimuru was supposed to let this demigod team go.
Whether to avoid punishment or to prevent Extraordinary Space from losing valuable fighting power.
If he had not yet advanced, then stealing it would have been no big deal. It would even have earned him the hatred of a demigod.
But now that he had already advanced, he did not think an Ego was worth earning the hatred of a demigod team.
Still, although Rimuru had shown goodwill, one thing had to be made clear: not stealing from them did not mean he feared