When James Charles, 19, became the first male face of CoverGirl, following in the steps of household names like Tyra Banks, Taylor Swift and Katy Perry, he was just a high school senior. In his hometown, Bethlehem, N.Y., he would charge friends between $5 and $10 to do their makeup for special occasions and had amassed a few hundred thousand Instagram followers by posting his eye-catching D.I.Y. beauty looks.

In the few years since, he has become an internet sensation in the beauty world, with 16 million YouTube subscribers (and nearly the same number on Instagram), his own merchandise line and make up partnerships, and a devoted following. He recently attended this year’s camp-themed Met Gala, the biggest party in fashion.

In a matter of days, everything changed. Mr. Charles is now at the center of an ongoing debate about betrayal among a passionate group of beauty vloggers, bona fide celebrities and the meme-makers of TikTok. He has lost about three million followers on YouTube; Miley Cyrus, Shawn Mendes and Kylie Jenner have all unfollowed him on Instagram.