Hunting and environmental damage could play a role, but I don’t think modern hunting/F&G policies could do much. They are very adaptable creatures and eat a variety of stuff, so I speculate you’d have to have real ecosystem collapse to cause them to bow out of an area.

End of the day for me - grizzlies ranged the entire country in 1776 times, and then by the 1970’s got boxed into Alaska, Montana, and Wyoming basically. If that bear disappeared/disappears, it’d be a tragedy. Meet a bear or see one skinned and they’re pretty darn close to human-looking. The Montana pop in glacier is about to join with the Wyoming pop in Yellowstone, they’re now in the bighorns in WY, and get spotted in eastern plains Montana now.

If you’re not hunting and dressing game, as most hikers are not, the main danger comes from surprising them, so just keep head on a swivel and carry bear spray. Carry a 10mm or .44 and up for if you get stalked by one. NOLS Lander has a good YouTube video on grizzly safety. After long enough accounting for this, I realized I wasn’t really “hiking” in non-bear areas much as marching around woods acting like I was, and I haven’t looked at the non-bear areas the same.