What would cause an application to suddenly start crashing upon launch?

I realize a definitive answer can't be reached here, but I'm just so curious: I've been using a weather app called Forecast Bar for years, downloaded from the App Store. Yesterday, I noticed its icon had disappeared from my menu bar, so I relaunched it. Fine. Earlier today, I used the app to check weather stats. Several hours later, I noticed its icon had disappeared from the menu bar again, so I relaunched it. It immediately crashed. Long story short, after trying everything from clearing caches, deleting and reinstalling the app, and restarting the computer (even in Safe Mode), it continues to crash immediately after launch. I've contacted the app creators, and sent them a crash log, but I thought I'd share the story here, too. Very odd, yes?