Until 1990 the Governor presided over Tynwald (and LegCo) so wielded more power than is the case these days and I guess therefore was in a position to steer things in a direction that suited HMG. Of course when the Governor was replaced in that capacity Tynwald went needlessly overboard and created the wholly unnecessary and overblown role of ‘President’ of Tynwald especially for Charlie Kerruish. His daughter, Clare Christian, subsequently exercised that office with a great deal more skill and judgement than either her father before her or the bumptious bag of wind Rodent who, regrettably, occupies the post now.
I don’t think the Treasury has ever been accountable to HMG but of course the AG and the Deemsters have always been, and still are, Crown appointments.
Of course, the conspiracy theorists (who may be on to something!) still see HMG exercising control over IOMG via the Chief Secretary who - in a Jekyll and Hyde existence - is principal advisor to both COMIN/CM and the Governor...thus running with the hare and the hounds (bizarrely).