this is a rehashing/summary of the much more in-depth research note by law school student Lina Khan that gained some attention earlier this year: https://www.yalelawjournal.org/note/amazons-antitrust-parado...

changes to the economic definition and legal enforcement of anti-monopoly are one issue, but a general slowdown in the pace of technological innovation combined with globalization/spread of technology is the primary force driving consolidation/horizontal/vertical integration in many industries