I bought 6.5 CM for the same rationale suggested in the OP.
Did I believe the hype or jump on the bandwagon? Not really.
There's nothing wrong with the cartridge and it fits a lot of people's needs.
So do dozens of other cartridges, but dealers don't have stock of all those chamberings (like 7mm-08, 260 Rem, 7x57), the factory ammo choices are limited for many, and even some types of reloading dies and components aren't offered for all.
If I had a 270 or 308, I wouldn't feel compelled to get a 6.5 CM, but I didn't have those. I didn't particularly need them to kill little deer either.
The momentum behind 6.5 CM is appealing. Not only can I find high-quality ammo like Barnes Vor-TX Long Range (LRX bullets) on the shelf (whereas in 270 I might only find boxes of stuff like Remington Core-Lokt), but I can also find premium reloading dies from LE Wilson chamber type seating dies, Redding micrometer adjustment neck sizing and seating dies, or the RCBS Matchmaster seater. Now I can find those dies for the 270, but not for the 6.5 Grendel or the old belted-magnum cartridges I already had. The 300 and 7mm are usually there, but none of the others, none of the Weatherbys. And as for Grendel, remember that's not an odd novelty. It's been around longer than 6.5 CM. It just didn't catch on as much.
How about quality brass? I can get Lapua in 6.5 CM, but not for any of the other rifles I have.
Bullets? There's no issue with 6.5 and 30 cal, but 8mm, forget it. I had an 8mm rifle. If that's all I had, then yeah, moving away from that to 6.5 would make sense. Even though I had two other 6.5's, adding 6.5 CM still made sense given the relative obscurity of the other two. Creedmoor also comes with more twist rate. Some older 6.5's won't work with lower drag bullets that are popular now for both match and hunting.
It's not just a bandwagon or a fad. There are rational reasons for the 6.5 CM and the momentum behind it makes it even more compelling.
If you've got a Swedish Mauser, there's no need to change it, but if you don't already have one, the whole industry today is behind 6.5 CM instead.