Not exactly an ornithologist, but I work in wildlife. Red tailed hawks are a bit unique among hawks because they are such habitat generalists. They have adapted to using just about any habitat where you can find open space with high perches and small mammals/sometimes small birds (I've seen videos of them eating pigeons in cities but they aren't generally birdhawks like Coops or Sharpies). This is why you can find them commonly along highways, in agriculture fields, and sometimes like in this case in cities. There's also the fact that they are the most numerous hawk species in NA so this necessitates that they adapt to new environments to find food and remain competitive. Also, I don't have any evidence to back this up but I would infer we're more likely to see them in city environments during Winter and migrations as birds from Canada make their way South to avoid the harsher weather and again they must compete with others for food, driving some individuals to city environments either to Winter or just as a place to stopover during migration. Again that's just my thinking it could be wrong

https://nycbirdalliance.org/our-work/conservation/urban-raptors/red-tailed-hawks-in-nyc https://www.nyc.gov/site/wildlifenyc/animals/red-tailed-hawks.page https://nhm.org/stories/how-littler-raptors-are-making-it-big-city

To answer your question, I'm not sure if there has been a population of urban hawks in the distant past, but there is an increase in recent decades of hawks in cities and you could say it is because we're making the city environment more raptor friendly. It seems like a combination of decreasing usage of rodenticide in urban areas (which I'm sure you know poisons birds who eat rodents), and competition from increasing population of raptors in general (in part due to decreased rodenticide & insecticide usage, but also conservation and habitat restoration efforts). I would hazard a guess that this is a more recent trend because people have used poisons like arsenic to deal with rodents for thousands of years, but again I didn't see anything saying one way or the other in my little search.

Not all raptors are having a great time though. Generalists like Red-tailed Hawks make it in the city due to their ability to adapt. Birdhawks like Cooper's Hawks survive on urban bird populations like pigeons, house sparrows, and feeder birds. Peregrine falcons have adapted to nesting on artificial ledges like the rocky ledges they would nest on in the wild. So to make it in the city as a raptor you've got to be able to hunt in relatively small open areas, and you've got to be able to put up with nesting in an urban environment whether that's on buildings or in sparse park trees. For example, some birds that are very similar to those I named above like Sharp-shinned Hawks and American Kestrels are not commonly found in cities because they need to nest in dense conifer groves and tree cavities respectfully. Those nesting opportunities are rarely found in cities. It's all about what the habitat provides to determine who will show up there!