Anyone can make a new instagram... just write some code in your free time, get (very lucky, and get) some VC to throw some money into your company, and you become a new instagram... then either get forgotten in a few years, or get bought for some huge amount of money. Instagram had just 13(?) employees by the time facebook bought them (or some other very low number, i forgot).
But a telco? No way... virual operator maybe, but there's no real money in that, but just starting to build basestations is impossible, you need millions and millions to even get frequencies, and you're already late for those, and there's basically no realistic way for a new mobile operator to come to an existing market now.
Yes, apple has a lot of money, yes apple can buy T-mobile, but for apple to build a tower in bumfuck alabama, that'll take years and years of bureaucracy and pain, and there are a lot of bumfucks around every country.
It's possible there's an extra $14/month in revenue going towards cell phones as an industry but due to the competition such as it is, it's mostly being spent on more aggressive GTM expenses.
I am not from US, but what I see from my experience there is one huge problem with mergers (besides all other): too big to fail. If you become systematical player like big banks and if you intentionally or non-intentionally get in trouble. You will be bailed out, not go bankrupt. This turns on God mode for Corporations, this create intention become reckless. If big banks would not be bailled out in 2008. Most likely we would see at least some kind of fragmetation.
This doesn't really add up. T-mobile's net income is 3-4 billion a year on 80 billion on revenue. They're not generating monopoly profits.
IMHO I don't think you can really merge your way into a monopoly. The existence of multiple companies to merge is effective proof that whatever business they're in is not a natural monopoly.
Look at social media as an example. Facebook is the dominant player but in the course of their existence Instagram, WhatsApp, TikTok, and Snapchat have all become billion+ companies while another dozen or so have made it to 100+ million. Allowing them to buy Instagram and WhatsApp didn't prevent the rise of Tiktok or the continued existence of Snapchat. There's no natural monopoly here and probably should be little concern to anti-trust regulators.
Compare with phones. You have a stable Android/Apple duopoly but it didn't come from mergers. It's a natural monopoly business so naturally monopolies formed. Facebook, Amazon, and Microsoft all trying to break into the market and failing miserably is also strong evidence. This should be a huge concern to anti-trust regulators.