I'm surprised no one has provided an answer to this. So I will share the solution I used for a couple years (I've since stopped using it).
Neat Download Manager. Be sure to install the related extension and look through the settings. This approach completely bypasses the Google Download manager and offers the bonus benefit of accelerated parallel downloads and resumability (if the file host supports it).
There are a few situations where downloads will not work with the Neat Download manager, in this case a tip for you, hold the delete key as you click a download button in the browser, and the download will commence via the browser's built-in download manager.
Cons
- It's not a beautiful download manager.
- Safari extension is not worth using (duplicate download in Neat + Safari built-in DL manager) Firefox and Chrome extensions are fine though.
- There is no way to disable, auto-clear, or bulk clear download history. It is tedious to delete every download in your history.
Pros
- It is lean for a Desktop application with a GUI.
- Does not require user intervention to download something.
I have no connection to the neat download manger project, and I have not been payed or compensated in any way for promoting them as a solution. I offer this simply out of my own interest for finding a solution to how Chrome's download manager requires user-intervention to complete a download.
I will happily select someone else's answer as soon as a better option comes to light.