Are you sure about CF Express? I thought it was the CF Association doing it.
You're right. In some ways CFExpress evolved out of XQD (which was already using the PCI Express bus), but it adopted, like CF and CFast cards before, the main storage access technology used on contemporary computing devices - it was PATA for CF, SATA for CFast, and now NVMe for CFExpress.
XQD used its own protocol, not a more standard and widely used one. Modern operating systems all support NVMe, so accessing cards won't need any special driver, ensuring better interoperability - and broader use.
Unlike the two previous standards that were designed for spinning disks, NVMe is optimized for solid-state disks (and cards) - and can reach far higher performance. If a camera needs to support faster storage access for more mpx, higher fps and hi-res. high-quality video, CFast will be soon enough a dead end.