Traditional point-to-point site-to-site VPN protocols require extensive setup in certain use cases. For example, if you want shortcuts between branch offices rather than let every packet go through the HQ, then you need to set up a cartesian product of tunnels by hand, which is time-consuming and error prone. So, people want something better, something easy to set up and maintain, and dynamic enough. While there are already a lot dynamic point-to-multipoint or full-mesh site-to-site VPN implementations (e.g. Tinc VPN, ZeroTier) on Linux, you don’t have many choices on these commercial black boxes.
Cisco DMVPN (Cisco Dynamic Multipoint VPN) is one solution to this. Huawei also had their DMVPN-compatible solution called DSVPN (Dynamic Smart VPN). Since the protocol is largely compatible, I’ll just reference it as DMVPN.