I agree however they couldn't help Renault either hence the row. It wasn't RB that started to turn the Renault corner it was Renault themselves. How then could they help Honda?
Also another reason could be what is in it for Renault to stay with RB?
Remember that RB don't even use the Renault badge, the RB affiliated team that does is aligning to an opposition manufacturer. No reason to stay if they won't even get any Kudos for a RB connected win.