government is an organisation of humans within a geographical region that work for the benefit of all the other humans within that region. it's as simple as that. it's the exception not the rule for there to be no private competition; unless you live in Cuba, in which case you're describing communism, not government
But that would probably be a negative for the same reason that bigger companies inevitably swallow smaller companies without government intervention: in the modern day economies of scale are everything. 10 companies that make 10,000 of something will generally lose to 1 company that makes 100,000. Monopolies will inevitably flourish without a strong government controlling them. (And moreover, in a globally connected world, if you kill all your monopolies it’s very possible another state that allowed their’s to flourish will have companies that can outcompete yours)
I’m not exactly going anywhere with this, I don’t have a great answer to what the best option is. You can try and force there to be 2-3 companies in every sphere…but that’s barely competition. You can try and regulate the massive companies…but almost inevitably large cash-rich employers end up with sway over the government. You can try for lots of local competition and shut out foreign companies…and lose out on the many benefits of free trade. You can try and cut a balance between all of the concerns, but it seems that whenever government tries for nuance it ends up creating a very expensive bureaucracy.