I just bought what was available. Common to these parts. I’ve never seen a 6.5 RM rifle before. The Swedes were mostly military sporters. The .260...I don’t know. I think the .264 Win Mag had a lot of admirers from afar, but in a lot of ways the 7 Mag was a better mousetrap and much more easily obtainable.
It took a revolution in bullet technology for the BC’s of a mild cartridge like the 6.5 Creedmoor to trump the speed of the 270, 25-06, and 243. And only recently have rifles and ammo become common enough for the average hunter to consider it.