It was forked in anger. A fair assumption is that there is at the very least some animosity on one side of the equation.
At the end of the day, people need a working environment and not everyone has the time of day to be updating every library out there that used a previously stable RubyGems API to use the new "better" ones (though I've yet to see a case where the API changes were little more than renaming a class and adding a couple class methods).