Isn't it meant to be a reference to biblical footwashing as a form of showing respect/deference? Trump washes Musk's feet, but incompetently/ineffectively, with his tongue. I fear that classing toe-licking as "sexual" rather than "creepy" or "weird" tells us more about the sexual preferences of the person classifying it than we really wanted to know!
https://religion.fandom.com/wiki/Foot_washing