How the sniglet took over, to the point where people use sniglets without realizing it. Sniglets don't appear in the dictionary, but they probably should.
The singular \"they\" is the Rodney Dangerfield of grammar, despite being around far longer than \"he or she.\" But is they close to mainstream acceptance?
It certainly wasn't the view. The British city of Scunthorpe has had a problem dogging it for decades, and lazy online programmers are to blame.
Words and grammar don't just show up in the dictionary or style guide by accident. Quite often, they're lobbied for—sometimes by super-rich people.