I haven't specified which island Bertie governs yet, but it will probably end up being Amboyna (or Ambon).
In those days, being appointed governor of an island like that wasn't so much about prestige (or, quite frankly, competence), it was about greed. Those postings were very very risky, because of the diseases and hazards associated with them, but they were also very very lucrative. So someone who gets sent out there is going there because they have that special blend of connections (to secure the appointment), risk orientation (because there's a good chance they'll die, most likely from a disease), and expendability (see previous reason). So you won't see someone like Cavendish going out there, because his family would never risk a senior son on such a venture, but the younger son of a noble or a retired officer (admiral or general) who didn't have a lot of money would be an ideal candidate.