Cheng Daqi, why did you start engaging in the identity business with Eris before you had taken down Gru?
For money!
The short video industry of Blue Sea Era demanded that he expand rapidly. It was inevitable that Shanhaiguan and MAS would find it difficult to profit in the short-term, but Cheng Daqi's career couldn't be confined solely to the short video field.
CEO Cheng needed a business that could provide him with cash flow, so he took the risk.
As for whether Eris would turn against him over money?
When Cheng Daqi started, he had thought it through. Gru's apprehension towards Temir was real at the time. He was certain that Gru would become a partner in his collaboration with Temir.
With Gru and Temir in the picture, the pressure from Eris's side became insignificant.
No matter the process, looking at today, the outcome Cheng Daqi had anticipated had indeed occurred.
It's just that to achieve today's outcome, both he and Temir had paid a significant price.