Then I was able to install it, and it said just start gvim and plugins will install automatically.
So I start gvim and nothing happens. Looks like normal gvim.
EDIT: allow me to be the change a little bit, if you install on windows, the fix: https://github.com/SpaceVim/SpaceVim/issues/3250
EDIT2: after the fix "E121: Undefined variable: g:_spacevim_if_lua" sigh
Spacevim is not an editor, that would be vim/gvim, which works fine as you said yourself. Spacevim is a collection of configurations, basically a plugin, and those are working on VS Code as good or bad as on any other editor.
Why would someone use this over Spacemacs in vi mode? (I’m sure there are reasons, just curious what they are)
As a vim user of 25 years before switching to Emacs+Evil, I can name only about two things. And they're not nearly enough for me to go back to vim for.
 - vim's \zs regex pattern, which would let me position the cursor ahead of where the regex match would normally take me without it. This can be very useful for certain macros, but I don't encounter an absolute need for it very often.. but when I do, I wish this was possible in Emacs.
 - In my experience, vim has been much more performant on large files with long lines.. but, again, I don't edit such files often enough to make me want to back to vim... and, anyway, when relatively rare cases when I do need it I can fire up vim for that one use.
Still nothing major, though.
I keep trying to use and learn emacs. It'll happen eventually.
One thing that's eluded me howver is being able to have graphical and terminal emacs work with the same daemon.
But when I tried Spacemacs it was just too much. It was completely overwhelming, I didn't understand where anything was, some key-strokes worked like Vim, some worked like Emacs, menus and commands and status lines appeared and disappeared almost at random and in the end I just gave up trying to understand this Rude Goldberg device.
Now, this doesn't mean that Spacemacs is bad - it's entirely plausible that I'm just not to bright and don't have a good attention span to learn this tool. But I don't think that I'm the only one.
Cursor in virtual space... Emacs doesn't do it right.