My thoughts: I started deer hunting in 1978, was hunting small game since maybe 1974 or 1975. Back east with guys frequented hunting camps in the north woods (now gone). And before a lot of hunting leases.
Have no idea how many millions and millions of formerly hunt-able acreage is now posted No Trespassing, a subdivision, parceled-off, or giant shopping plaza. Where I grew up shooting squirrels, rabbits and pheasants is now a shopping plaza, my folks bought some land and we hunted/fished/snow mobiled/etc. thousands of adjacent land that is all posted and much of it was divided into 5-acre lots. Hard to snow track a deer across 20-25 5-acre lots with cabins on em. Deer still cross thru mom's land but before and after, we can't pursue them due to neighbors saying "no".
Folks are now traveling cause hunting around home often sucks and there are other places to see and experience. FL is a nightmare for me to try and hunt cause the places I want to hunt and the little 3-5 day hunts cost 3-5 preference points. So, wait 3 years and get to hunt 3 days. Nutz. There are other opportunities, but if I'm gonna drive 2-6-8 hours across the state. I'd rather go out of state. Used to lease in GA and SC but finally realized what it actually cost me and said I'd rather go elsewhere for that money (bought a boat - have about $1,000/year left over from my hunting budget after making the payments and putting gas in it - go figure - saving up those $1,000's for when my time comes with WY speed goats again.)
As for hunting out west, IMO, GPS with onXmaps is the single biggest reason for the explosion of folks going. Before, there was always the threat of the trespassing issue, and how the locals and LEOs frowned on NR hunters getting on the wrong side of some imaginary line in the middle of a field or mountain side. We actually considered that stuff when thinking about taking the trip and decided that it wasn't worth the risk 1/2 way across the country.
So - we have loss of places to go (camps), loss of private hunting land, no trespassing signs, explosion of hunting leases, increased pressure, less game on public land, Quota points to get a simple license close to home - or across the country, etc. Technology also opened up what was formerly foreboding and difficult.
Then we get into the idea that if we can't hunt around home, let's go somewhere with more and diff opportunity. That shifted pressure to what folks enjoy whether it be birds or big game or small game/prairie dogs.
The internet and you tube has surely affected what folks see and use in their decision making process. It is part of the puzzle but not the sole reason.