Default Gateway and VPN's

This is kinda infuriating and funny so let me explain.

6 months ago i purchased VPN service and chose IKEV as my protocol of choice. I manually setup the connection with my VPN providers username and password. The connection would establish itself but each browser I used and each IP verification site I visited would show my actual ISP's IP, in other words I thought I was unprotected and stopped using IKEV.

Literally 15 minutes ago I had a remote session with a the VPN company, something I had done several times in the past, and they simply went into the ipv4 settings and ticked 'use default gateway on remote server' and BAM my IP was showing up correctly on all sites I tested.

please can someone explain to me A. what the heck happened and why was that the solution?
B. why did not a single tech at the VPN provider come up with this solution in 6 months and multiple tickets?

thanks!

Default gateway is like the door to the net normally your router if it's set to use that everything goes via your router and standard ISP IP. Gateways can have a matter set of which is priority. By default you get IP from the router along with gateway

thanks dude