You don't need a VM to compile something into Javascript but the VM buys you a fast edit/reload cycle and some tooling like a debugger. Also Dart can be used as server-side language and there the VM makes sense. It can also be used as an interpreted language just like Python and here it doesn't hurt if it's fast.

Even if _you_ don't put type annotations in your code, the IDE infers types (locally) and gives you useful warnings and code completion.