Computers have conquered scale. Before cheap computing and networking, large companies had trouble getting out of their own way. There were inefficiencies in companies that got too big. Most of those problems seem to have been solved, and the intrinsic limits to corporate growth have been removed.
So now the US has three big banks. Three big drugstore chains. Three big delivery services. Three big cell phone companies, if Sprint and T-Mobile get to merge.
Big companies don't have to have regional subsidiaries any more. In the Bell System days, AT&T had about ten regional operating companies, each with somewhat independent management. Today, they don't bother. Amazon is run as one big company.
In the US, government hasn't really gotten into this in a big way. Too many governmental units with their own local authority. China, though, or the UK, where the central government has total authority...
(This is not about Trump. He's an old guy who does things the 20th century way - broadcasting to large numbers of people and hands-on project management. When we get someone who's similarly authoritarian but understands modern scaling technology, we'll have a real problem. Peter Thiel, maybe.)