It's really common for people to assume scientists are white men.

A newly published University of Virginia study has found that about two-thirds of students in a third- through fifth-grade extracurricular astronomy program perceive scientists as white men in labs, mixing chemicals – even as women and people of color increasingly work as scientists.

The study authors found that these perceptions persist even after elementary school students have been tutored under young female scientists in a program designed to increase understanding of and exposure to astronomy.

Here's another study on it:

We found that the scientist image was rated predominantly as White and male, which reflects stereotypes about who pursues scientific careers. The scientist image was also rated more negatively than the other CIs on several characteristics, which may indicate negative biases toward scientists as unsociable, poor communicators, and incompetent authority figures, especially during the COVID-19 pandemic.

This isn't a made up phenomena just for social media. It really happens.