It isn't, but there really isn't a need for them to step in and block the deal? Is it their role to ultimately force one into bankruptcy? That is kinda what they did by blocking the deal. There were similar concern about XM Satellite Radio and Sirius. Neither was profitable on their own and they almost filed for bankruptcy after the merger. But the merger probably saved both companies. At least for a period of time. IMO there isn't a need for the government to intervene at all. The marketplace will work things out.
I'd argue that because we didn't live during the 1880s and the "golden age" of monopolies, we don't really viscerally know that the market in fact
won't work it out - but history kind of implies that. The question to me is - you will always have companies wanting to create a monopoly - or get as close as they are allowed / can. This is at least partially because during the "trying to become a monopoly" economies of scale are a competitive advantage.
I'd argue another related issue we've started seeing since the pandemic, but came up again with Hurricane Helene and to some extent in the airplane duopoly - Even if pricing is regulated or under control for whatever reason, having geographically highly concentrated or single company and therefore often single geographical location is a huge supply chain risk. If the only place that makes chips is taken out for some reason, or the 60% or more manufacturer of saline solution is hit by a hurricane - whole parts of the economy just stop or people can't get needed surgeries. The market isn't sorting this out, and probably won't because in "normal times" there's no ROI to even trying to compete, and as we see with Airbus - they have so many orders they have no interest in trying to take market share from the struggling Boeing. And at the huge 1-3 manufacturer level - they won't respond to any supply disruptions to try and run another factory line or take market share unless they see like a 20 year change.
However, if you've got lots of competitors, in lots of regions, this doesn't seem to happen - take something like Car Repair or cell phone manufacturing. If Apple stumbles, Samsung, Hueweii, ZTE, Motorolla, OnePlus and more are all ready to make a few more phones, and at least some of those are made in Korea rather than China. But even there - most regions have some interest in having cell phone options closer to home also - in case there is another major disruption.
We can argue the effectiveness of various government interventions, but I at least don't think the Microsoft IE reign OR the insulin debacle is actually "the market working" in terms of consumers - which I would argue is a major reason we have an economy or market at all - to get consumers things they want or need.
