I believe they agreed to this deal after they combined their two compounds and found something we haven’t been informed about as of yet. I also believe Charles has every loose end secured and Harry is very happy with the deal. The more we dig the more we will discover.
Why would he leave? He had many years before Charles and how did that go? They merged for a reason. The treatments on their own were good but combined could be great. Harry knows this is his chance to make it finally