Pretentious Anger.

World gods can do so much more with cosmic energy. And only a very strong world god can have as much Cosmic energy as Legion. A strong world god in possession of a lot of cosmic energy and at least a universal artifact makes Legion an entity that she doesn't want to mess with. She will rather watch the clash between it and the first Sage. So her display of anger is just for show. She doesn't actually plan to interfere in the competition. But appearances matter. 

She hates the Sage, so she should hate Soverick. Therefore she should be angry, and her descendants will be angry with Soverick. But she won't interfere herself because she seems to fear the Sage. It is all according to what the first Sage will expect of her. She doesn't want to behave otherwise so as not to make him suspicious. It wouldn't do for the first Sage to dig too much into things and find out that Soverick is an imposter.