One huge national company in any industry simply needs fewer support people, customer service people, lawyers, accountants, custodial workers, etc. than the same geographic footprint served by multiple smaller businesses.
That's fundamentally a good thing - less labor is required in order to create the same product, so the world is richer.
The problem is that the resulting wealth is more unevenly distributed. But inequality can be fixed by using a more progressive tax system and providing a social safety net. That is a much more productive approach than trying to preserve redundant jobs.