Those three companies have about $90 billion in cash on their books. McKinsey & Company calculates that the largest software and hardware companies have enough excess cash on hand to buy nearly all of the tech industry’s medium-sized companies.

As long as there is this kinda cash sitting with companies wanting to buy, there will be companies made. Cash is cheap nowadays and there are lot of people/companies willing to bet.

mobile tech, wireless access, cloud/aws, linux maturity, etc.. - everything culminated to make whole tech companies so disruptive, no other field is ripe with products or speed of innovation.