We still had more scoring shots than Brisbane before the McInerney injury, and less than them after it though. Holmes was close to BOG in setting up our lead and the second he went down we started haemorrhaging scores.As much as I agree with you on Stengle (and also on Holmes' injury, to be honest), it's worth bearing in mind that McInerney was starting to absolutely take us to the cleaners when he got injured.
But if we set that aside, a crucial difference was merely Brisbane's small forwards being clinical and efficient in crucial second half moments, while our elite fleet had a haphazard or ineffectual half of football.