Can you please expand upon this?
I've seen plenty of people claiming that Hawthorn's run of success is due to the expansion clubs and free agency, but I've yet to see any convincing argument about it, or any details or evidence put forth about how exactly this has benefitted the Hawks.
People just seem to be mindlessly echoing each other and convincing themselves of this "truth".
Exactly - one of the "theories" from supporters that cannot bring themselves to credit Hawthorn's achievement and recognise that they are one of the best run clubs on and off the field. This "expansion club and free agency" claim has been rolled out without any level of explanation (i.e. Club X would have drafted player X and their team would likely defeat hawthorn in year X). You only have to look at the strategy adopted by Hawthorn to turn over their list (out of necessity) after the 08 flag to realise its a case of superb list management that had Hawthorn contesting Grand Finals in every year since 2012.