Use USB hub without power

I have a USB hub I want to use to transfer files from a CD card (inserted into a card reader) to an external portable SSD.

https://photos.app.goo.gl/i5jCsAmimMVkRDDt7

If I connect the hub into my Pixel 10 XL Pro the Google file manager will only recognize either the SSD or the CF card, whatever I insert first.

If I use Solid Explorer, it will recognize both but then when copying files from card and pasting into SSD the copy fails, unless I power the hub.

Any reason why I need to power the hub?