KG
Fewer lines of code
A little more research gave me some insight into why Torvalds might have been so uncharacteristically positive. WireGuard weighs in at around 4,000 lines of code; this compares to 600,000 total lines of code for OpenVPN + OpenSSL or 400,000 total lines of code for XFRM+StrongSwan for an IPSEC VPN. Two orders of magnitude fewer lines of code mean a lot less attack surface to find flaws in.
https://arstechnica.com/gadgets/2018/08/wireguard-vpn-review-fast-connections-amaze-but-windows-support-needs-to-happen/