I tried voting on this, and Facebook's own voting system kept failing on some or other unspecified technical "error", so I wouldn't entirely blame apathy, and apathy is also engendered by not bothering to have a working technical system for voting.
I also got the email and attempted to vote on this - and got the same voting 'error' you describe; knowing now that I was not the only one to experience this, has me wondering whether Facebook was more interested in seeing the voting process itself fail.
"The pyramid is opening!" "Which one?" "The one with the ever-widening hole in it!" -- The Firesign Theatre