How does one make other Guild members Leaders?

Don't. Only have one leader and make 1 or at most 2 others (to cover for holidays) Right-Hands. They have the same rights and priveleges that a Leader has.

If your leader has become inactive submit a ticket asking for them to be changed and clearly stating who the new one should be.

if yor leader has not logged in to the game for 7 straight days the game will automatically promote the next highest person in command to be leader. If two or more are RH it will then go down to fanbases . Hope this is useful

but the leader cannot make other members leaders too

This is a new one on me. Have you seen this happen? Are you saying the leader is also replaced or do you then have two leaders ( which I have seen in the past ).

The leader didn't get replaced we just had two leaders for a little while before the original leader of the team left at random without saying a word but if your leader doesn't login for 7 straight days your nearest RH will end up as a leader. He can be demoted when the original leader is back . I only know this from running a guild on the football where I am a leader and when I go on holiday i sometimes comeback to see there is two leaders.

Also if ur leader wants to step down u can make the team u want to Be the new leader the only right hand, then the original leader leaves the guild the only right hand becomes the new leader the old leader can then re join the guild