If the artist (or someone else) has to explain (not interpret or explicate but explain, as in "this is the right interpretation and this is the wrong one") the work then it has failed. Regardless of however much one is or isn't fluent in classical studies or Greek mythology or fine art or Rupaul's Drag Race, the point of the work was lost and that's the artist's fault, not the fault of the audience.
When you release your work for public consumption, you don't get to decide how it's digested. Blackface minstrel shows in the early 20th century in America, to use one example, might have been an homage, one could argue, to the animatedness and musicality of Bl@ck American culture. But that's not how it was received and that's not how it will be remembered, at least so far.
If I were the artistic director of the opening ceremony and my inspiration was Dionysus and the Feast of the Gods, I would have been very careful to make that abundantly clear and distinct from any resemblance to a drag version of the Last Supper UNLESS I wanted this controversy to ensue to rile people up and get noticed. The two works are not similar. But one is far more iconic. And while the Olympics are obviously Greek in origin, the ceremony should be a distinctly French performance, and imbued with French cultural references. So with France being a largely Catholic country, it makes perfect sense that people would see the tableau as a reference to Da Vinci's Last Supper. That's a perfectly legitimate interpretation.
So artistic director Thomas Jolly either wanted to stir up some kind of mixed message so that he could clap back and make people feel ignorant or he just didn't see how his own work could be misconstrued, which would mean he failed at his job. I'm not entirely sure this wasn't some form of trolling on his part and that he isn't having his own Dionysian bacchanal celebrating the backlash to all of this as we speak.