Probably to do with the following resonably standard policy terms-
'The policyholder shall at all times use due diligence and do and concur in doing everything reasonably practicable to avoid or diminish any loss hereon'
or
'The policyholder shall comply with all air navigation and airworthiness orders and requirements issued by any competent authority affecting the safe operation of the aircraft'
These terms or very close approximations of the same are most likely tucked away under the 'Conditions Precedent' of the Insurance policy and given the blatant and public nature of this accident it seems highly unlikely that any claim for the hull would or should be entertained- this might be different if the Assured party isn't flying the helicopter i.e he has loaned it to a friend but either way it's gonna be a stinker of a claim.