Though collusion between two tech giants is obviously distasteful and anticompetitive, how is this ultimately addressed? Sure, governments could force Google and Apple to break into smaller entities...but as long as humans still largely choose the best software, there will still be network effects that lead to dominant players emerging. In turn, there will be new giants.
So...either there are general paradigms/regulations/principles to apply, or we'll simply return to this state repeatedly, no?