There's two sides to this.
1. That's because it's true. Creatine is extremely well studied and the studies pretty much all tell you that Creatine is safe, it's great at what we know it's great for, and it turns out it might be good for things we didn't expect. So when people all say "wow it's so amazing" they're right.
2. Because of (1) being so blatantly true, if you want to push some other supplement, it adds a lot of legitimacy to say "Creatine is the number one supplement, but here's something that takes things to the next level". Since the Creatine claim is well supported and you're already marketing to a group that's taking a supplement (Creatine), it is likely good marketing to piggyback on that.
But this doesn't change the fact that Creatine is shockingly well supported as a supplement.
For me, besides creatine which has been genuinely transformative at age 50, I've gained a lot more from the stuff I've dropped (dairy milk, ~2/3 of my caffeine (mostly by drinking reduced-caff coffee or tea and eliminating soda), sweets of course) than stuff I've added. But of the latter, I'd say fiber and fruits have been the biggest additions, partly in themselves and partly that they make it easier to avoid the bad stuff. I tried experimenting with a few other supplements, but most of them were meh at best.
So, "take things to the next level" with some pears and oatmeal and chia seeds! Now I just need a sponsor.