I hesitate to posit myself as an example, but I was out of academia from 2001 to 2019, when I decided to become a stay-at-home dad while my wife became the breadwinner. (I won't go into the details of why I feel our decisions were the correct ones, but I'm satisfied they were.)

For a few years I didn't do a whole lot of mathematics, but it's never left me entirely. I began to get slightly more involved around 2004, especially after seeing some of my earlier work talked about. The n-Category Café, MathOverflow, and the nLab became important to me during the years 2006-2019; they kind of kept me going, as I carved out time to do mathematics. I didn't do research in the sense of writing papers (at least not much), but these activities nevertheless helped me keep some of my tools sharpened and to continue learning mathematics.

In every such case, whether it be Villani or myself or anyone, I think it's possible to return to mathematics research, if the sirens keep calling and the mind is still fit for it. In such cases, it's mostly a matter of desire. And, of course, time.