Used to be a lot more oak woodland, prairie, open conifer forest, broadleaf riparian forest, and other good blacktail habitats before suburban encroachment, intensive forest management, wetland draining, more and more roads, fire suppression, etc., etc., not to mention more hunting pressure.
I've seen a good number of blacktail antlers from the 1960s and before, and they have mass and size that would be notable today! I'm glad there are still some big bucks out there today.