The Big Tech companies are big because big companies are the ideal in the specific context of the tech industry and given the specific needs filled by Big Tech. For example, Facebook allows people to build and maintain social networks, a purpose which is best served by having a single platform on which all social networks are hosted and integrated. Nobody wants to have to track down segregated groups of friends, family, and social contacts on a variety of competing social network sites. If each person's social network was dispersed across a group of competing companies, the end result for the consumer would be messy and redundant in comparison to what a single large company like Facebook can offer.
[P1] The size of Big Tech companies ensures that they are able to supply the services people want. [P2] Their size is an asset, so they should not be broken up.