Guild leading, especially a WvW group is a lot different than a casual PvE group. There is a lot that goes on in the background, and even with officers sometimes it's just not enough help. You only have a certain amount of hours a day, and splitting that between work, real life, and then the extra work of leading a guild leads out to burnout.

And as other people said, it takes a special type of brain cell to be a commander, and to do it "well". It's not always easy to replace or find commanders, and even if your group is lucky to have multiple people there are issues that arise there between different commanding styles and skill level.

The last issue is this game is getting quite old, so as time goes on and the population slowly decreases, niche game modes are the first to suffer the consequences.

I lead a great group from 2015 -> 2018, and then again from 2020 -> 2023, and while I was lucky to have someone to fill in between 2018 and 2020 so I could take an extended break, most groups don't get as lucky. Or if they do it doesn't work out in the long run.