IT infrastructure has nothing in common with this aside from ISP.
Really, given that this is a market that is growing double digits by year, the amount by which amazon dominates it is shocking.
And that is in a market that is still growing rapidly. For Facebook/Whatsapp this is even more obviously not true. Facebook even failed to leverage its social network monopoly to establish its messenger against insurgents, simply because they were a bit late.
The idea that economies of scale make it impossible for a company to never face competition is ridiculous. The only thing that can do that is govenment protectionism.
Along with economies of scale is the opposite effect: the inefficiency of bureaucracy and having competing interests between business units.
Being large isn't the magical unicorn you think.