The X-Men are a pop culture juggernaut, which feels ironic for any fans who know the franchise's history. There was a time before the MCU when the X-Men were the most popular Marvel characters in the land, with even Spider-Man falling behind them in sales and popularity outside of comics. When many people think of the X-Men, they think of the teams that debuted in the '80s, '90s, and the 21st century, mainly because the Silver Age X-Men weren't popular at all.
Source：https://www.cbr.com/xmen-1963-why-matters-marvel-comics/
