Ironically, people move to bigger cities because they think bigger cities provide more social opportunities. But bigger cities are full of weak social tribes and transient people with no social life.
I think you have to examine who is moving from smaller cities/towns (150,000 people or less) or mid-sized metros (150,000 to maybe up to 1 million, the upper bound on mid-sized metros is debatable) to the metros of 1 million or more people. I think it is often the people who are struggling socially in smaller to mid-sized metros.
The guys who I have seen do the best in the early stages of dating (from the initial meeting through roughly 1 year into a relationship) are the guys in midsized metros who are geographically fixed. These were guys who had the fortune of spending all of their 0-18 years in the same area and then staying in that area as adults, possibly only leaving to go away for a 4 year BA/BS degree. Because they are in midsized metros, they don't suffer from having too few choices but the metro areas are not overwhelmingly gigantic and have weaker social tribes. I think the sweet spot on metro size for dating is 200,000 - 600,000 population. Now, some of these guys in midsized metros who are geographically fixed are actually blue pilled guys who are somewhat boring and have gotten divorced, but many bounced back well from divorces due to the strength of their social circles. In big cities with weak social tribes, these blue pill guys would get eaten alive, but in their midsized metro cocoon with a social circle, they do well. Their individual strong ties to the region and less hypergamous female behavior (partly tied into smaller, more connected areas) help them and they don't have to study seduction and attraction to the level of a lot of big city guys.
On a separate note, one of these guys actually turned down a great job in a big metro. When this happened many years ago, I thought he was nuts to do that. As time went on, I realized he had an inherent understanding of the value of his social circle in his midsized metro.
Generally speaking, very few people relocate to these 200,000 - 600,000 population metro areas, especially from out of state. If these metros get migration, it's from people in the same state/region in even smaller cities/towns.
Since my graduation from college 15 years ago, I have lived in two Top 15 in population metro areas of the United States, neither of which are close to places I lived during my 0-18 years. They've been weaker social ties cities, meaning that I have needed to possess stronger game and stronger frame than a socially well connected guy in a smaller metro area. You're really correct about the nature of these large metro areas.
When you examine who is on swipe apps in larger cities, a pattern emerges for both men and women. After age 27, the men and women on the swipe apps are people who did not grow up in that larger city, have typically moved a few times as adults, and often had transient childhoods. The female natives to a larger city that are often on swipe apps after age 27 either have a divorce to their name and/or are single moms. If they don't have a divorce to their name, they usually had a 5+ year relationship from either high school or college go down the tubes.
It;s funny you mentioned this. Gaming in smaller cities while working summer jobs back in college was how I learned about social hierarchy game. I took an internship in a rural small town and found that social networking game was way easier than in large cities. Everything had a sense of gravitational pull to it. Like status was set in stone. Status in a large city appears more transient like quicksand. This is why big city gaming is so hard for guys who don't have bulletproof frames.
In a small city, I befriended the town bully that kicked everyone's a$$es and ran a circle of 10+ women. The guy literally used his physical strength to dominate an entire town. He probably couldn't get away with it in a larger city. But he was massive for a short guy. Probably 5'7 but 225 lbs of solid linebacker muscle. Sort of like a prime Mike Tyson physique. One day he showed up to a social gathering and said "Fvck it, everyone is getting laid tonight" and left and came back with 10+ women. And everyone did get laid that night.
Another gatekeeper I met was a guy name Alex. His family owned an entire restaurant chain in the town and adjacent towns. He once showed me his pic collection of women he'd fvcked and it was a massive collection of over 100 + women bending over on his bed, including married women and some women I knew from work. I quickly became his best friend and he saved me from scavenging around past 11 pm at the neighborhood bars. I went from a social nomad to spending the summer going to beach houses and play wrestling with cute chicks. There was no GAME involved.
These are all relevant anecdotes that illustrate some of my points from above.
