David Frum, in The Atlantic, views that as a fitting metaphor for Pence's tenure as vice-president:
We saw a weird moment when a fly landed on Pence’s snow-white hair—and the vice president did not react at all. No doubt, it’s a conundrum, what to do in such a situation. If Pence had shooed the fly and the fly had refused to shoo, that would have been bad. So he did nothing. And that doing nothing somehow in one powerful visual moment concentrated everything. It symbolized the whole Pence vice presidency, the determined, willful refusal to acknowledge the most blaring and glaring negative realities. Through all of the scandals and the crimes and the disasters of the past four years, Mike Pence was the man who pretended not to notice. And now there was a fly on his head, and he pretended not to notice that too.