In addition, even if they had set up Let's Encrypt auto-renewal, they may have had to shut down the system running it before they left. Leaving a system up that

In addition, even if they had set up Let's Encrypt auto-renewal, they may have had to shut down the system running it before they left. Leaving a system up that you won't be around to patch/maintain is almost always worse than shutting it down until you get back.