"Explode" is a pretty strong word for a technology that was somewhat stillborn. Yeah, it showed up on Solaris as Solaris was winding down. I've never seen it used anywhere, and I've been doing this for awhile.
The classic use of ZFS was on the Kealia / Sun Fire X4500 "Thumper" box. 96 TB in 4U in '06. It was a beast and worthy to throw rocks at NetApps.
Anytime someone insecurely touts "I've been doing X for Y years," I know they've reached peak complacency rather than continual learning and mastery.
I'm in the semiconductor industry and we used to have thousands of SPARCstations and SPARC servers for larger jobs. All of the EDA (Electronic Design Automation) tools ran on Unix / X11. Around 2002 the vendors started porting some of the tools to Linux / x86. The machines were faster AND cheaper.
By 2003 the only jobs run on the Suns were processes that required >4GB RAM. When AMD released their 64-bit x86 Athlon CPUs we bought some of the first ones. After that the Suns just faded away.
In the 1990's all of our file servers were from Auspex. We have been using NetApp fileservers for about the last 20 years. Other than a few scratch drives I don't think we ever used Solaris as a file server.
The university I worked at had a large Solaris deployment for internal IT systems for the CS department. They kept it for many years because it worked, it was a known quantity, and was reliable. They could've changed it over to commodity boxes running Linux or FreeBSD sooner, but that would've been a major headache for downtime, costs, and staff processes.
A friend-of-a-friend ran an extremely large deployment of Solaris boxes for batch jobs of a military data processing facility.
The scariest SunOS feature was metadisks: striped drive volumes to expand storage.
I'm not insecure, and I'm not mad at ZFS. I'm just pointing out that it showed up when Sun was already circling the drain.
Seamicro managed to pack 2000 cores into 10U. Cool. I've never seen of those, either.