Not totally new
IOS-XE and NX-OS were both designed to run in user mode space on a Linux kernel.
Both had been available in virtualized forms for years: The Nexus 1000V VMware virtual switch ran NX-OS, and the CSR-1000V virtual router runs IOS-XE. CSR-1000V can run on VMware, KVM, Xen, Hyper-V, Azure, and AWS.
While VMware's decision to no longer support third-party virtual switches ended Nexus 1000V's role, the CSR-1000V is popular as a way to provide OTV services without needing an Nexus 7000 or an ASR.