“Fun Home” was the decided underdog: a nominee with little money, bold themes, no frills and a small team on the payroll. (Sound familiar, Sanders-ites?) The story of a lesbian cartoonist and her relationship with her closeted gay father, “Fun Home” is about facing difficult truths and the tragic consequences when we don’t — the very message, as it happens, that the Sanders campaign is offering to America about income inequality and climate change. Compared with the flashy big-budget musical “An American in Paris,” which was the safe bet to win the Tony, “Fun Home” looked like a fringe contender, too dark and offbeat to have wide appeal, not unlike certain politicians who are easily dismissed as quixotic nonfactors.