Why does the power bank have a DC connection if you can't charge the laptop with it?

If you have USB C Powerdelivery on your PC then I would suggest digitec USB-C - USB-C (2 m, USB 3.2 Gen 2x2), I have had good experiences with this.

If your PC has a USB-C. Power Delivery (PD) which can receive 100w it can be recharged via a compatible usb cable.
Otherwise, you need the charger