I've seen this discussion in many places before and fact is, chess doesn't meet all requirements of our current definition of a sport, because it doesn't include a significant aspect of movement, but at the same time it is legally and officially a sport and enlisted in the olympic sports. Yes, this is a contradiction - and there are many potential reasons for it. One might be that most of the national chess organizations are a lot older than the national sport organizations and therefore at the time when they were founded (and the definition of sport was a different one) they were included too.
It is correct that chess lacks a strong physical component in the game, even though it is very challenging regarding endurance, like other sports too (I know that too, I've been playing 5-hours chess tournaments for several years). At the same time also other sports are not strictly physical, they all have a mental component, regarding tactics or strategies. Some more, others less.
In addition chess meets all other requirements for the definition of a sport, especially the competitive character, organization (teams, clubs, leagues, tournaments and so on), strictly defined rules, and last but not least also aspects like the non-randomness of the game.
This would btw also one reason why Elements can't be a sport - it has also lots of random factors that do not depend from the human, but a machine (the computer).
In addition what I wrote initially (chess is officially a sport even though it does not match the current definition of a sport) prevents any other boardgame like it from becoming an (olympic) sport.