I guess that elk must've taken to using steroids. Back before magnums were all the rage, hunters were killing everything with the 7x57, .303 British, .30-30 Win, '06, .45/70 Gov't, .405 WIn, etc. Not these cartridges won't work on jackrabbits.
When I was a teenager, my dad told me that there was a time when the .300 was the .300 Savage, which was plenty gun for really big critters.
Biology will always win. Nothing lives sans its heart. Period. End of story. What destroys it is immaterial. That it is destroyed is.
A confident hunter who puts a 100 grain .243 Win bullet through an elk's heart will kill it just as dead as were it shot with a super duper mega-magnum. After all, dead is dead.
What a hunter uses ain't nowhere near as important as his ability to use his rifle.
There's another sage old saying: the hunter who owns one rifle knows how to use it.
