If you ever ran into an issue of having two network card and wanted to make one as primary, nmtui can be a handy tool.
Ideally defining GATEWAY to one of the network interfaces would solve the problem but this situation is ideal when one has static and other has dynamic IP or both have static IPs. My situation was even complex when I had both the interfaces get its config via dhcp. In this case I really cannot control which interface should have the GATEWAY defined and which not.
With the help of nmtui command, i could tweek the network interface settings where I selected the below option for all the interfaces accept the primary one:
Never use this network for default route
And that was it. Hope it helps someone needy.