when was chess most popular


I don't know about the rest of the world, but in America computer games have greatly hurt the numbers playing board games, reading books, getting interested in astronomy, writing, etc.
In America, the membership of the U.S. Chess Federation tripled after Bobby Fischer beat Boris Spassky for the World Championship. It has declined since, mainly because the USCF was much more interested in attracting foreign players to move to the USA than in developing U.S. chessplayers who they ignored almost completely and misled them by advertising books with phrases like, "Play Bobby Fischer's Openings and win like Bobby!" - instead of pointing them to learning chess principles.
I served as an unpaid USCF tournament director for Scholastic Chess and a high school coach and yet only my state organization helped me develop players. I was running low-cost tournaments and USCF must have figured they couldn't suck enough money out of the teenagers pockets, so helping them wasn't good for the USCF.