I don't think you can keep talent in one place forever. Western culture is a little different these days where it is a job for life. People tend to take that leep and change now and then. Besides they were there for a very long time together anyway.
To me they just wanted to try something new and a different challenge.
The only reason you would keep RARE was because of the IP they had not so much the staff that was left. Nintendo should have realised that and bought them out and injected new talent into that studio.
Those IPs with the right young talent and Nintendo's guidance could have been amazing.







