How do you become a club leader if the past club leader abandoned the team?

We already have an answer for a similar question which you can see here:
How do you remove a club leader?

If you have more answers to add you can do that below.

You can message the game administrators through the help feature in settings and inform them that the Team Leader has abandoned the club and ask for them to pick a new Team Leader. Give them the name of your club, who the current Team Leader is and who you want to be the new Team Leader. They will investigate and see when the last time the current Team Leader participated. If they think it is warranted, they will remove the current Team Leader and choose another. That’s how I became my Team Leader. The former leader had not logged on in 6 months and there were no Officials, after a week in the club I was Team Leader and promoted 6 Officials.

The only thing you can do is announce to your group that you are going to create a new group, or ask someone else if they would like to create a new group. Create the Name of the new group before leaving your current group so anyone who wants to continue to play with you can find your new group name in the list of groups. I had to do this.

Come up with a new team name for your club and announce it to everyone before you leave the group, then go and create the new group so the rest of the club can find you.

Inside the game, in the Play section, click the settings wheel on the bottom left corner. Go to SUPPORT tab and click SUPPORT button.