How much tread is left on the other tires? (I’m trying to get a sense of how much faster the right front tire went.) It sounds like you don’t ever rotate your tires. Is this correct?
As others have said, it’s a little surprising that a tire could get to this state without being noticed. You really do need to look at your tires more often (and probably check your tire inflation far more often, if I had to guess). If you ran these tires last winter in Maine, count yourself lucky that you didn’t have an accident.