It’s always been popular among athletes and weight lifters but now nootropic influencers have gotten ahold of it. It’s one of the few supplements with robust scientific evidence of a strong effect but that’s in athletic performance not nootropics.
No, creatine has been studied for decades and it’s been part of fads before (I remember Mac making a joke about creatine shits in It’s Always Sunny in Philadelphia a decade ago).
It’s just resurfacing as a general health fad/marketing campaign.
JRE mentioned it several times recently, I imagine it could have spiked interest but overall it's been growing over the past decade because of the advances in fitness trackers, IMO. It's been very easy to see its effect with trackers measuring FTP and VO2max.
I've been taking 5g/creatine daily for nearly 30 years. In weightlifting circles it's always been popular because it's cheap and one of the few non-steroidal supplements that actually works.
Creatine is a health fad? No other supplement has been this widely-used for such a long time. It was considered safe and effective when I started using it 30 years ago. The benefits are/were well established, the mechanisms well-known, the safety is impeccable. If anything, it's the most well-established supplement on the market - the exact opposite of a fad!