Why FiveM runs well here
FiveM leans hard on single-thread performance. The server tick that runs your scripts, resources and player sync does not spread itself across many cores — it wants one fast core, and it wants that core to itself. That is the whole reason every Noctis plan sits on AMD Ryzen Zen 5 rather than recycled shared hardware: the entry vDedicated gets the same modern single-thread performance as the largest one.
The second half is contention. A typical VPS oversells its host — your cores are shared with neighbours and get contended exactly when everyone is busy, which for a roleplay server is prime time. A Noctis vDedicated reserves the cores and memory on your plan for you alone. Nothing is shared away, so a full server behaves the same at 9pm as it does at 4am.