I take it you forgot Whom Gods Destroy?Really - in the TOS timefarme they couldn't really rewire Pike's brain. In fact there's a specific line regardiong that aspect from TOS - The Menagerie itself:
And ST: D is 10 years prior to that episode - and the events of TOS - The Cage is 2 to 3 years prior to the start of events that will be depicted in ST: D.