lol, hardly any of them will be full time professional chess players. Only the top handful will make all their money from competitions. Some are partly supported by chess federations which are often government funded as chess is seen as a prestige game in some countries. For you to equate being a Fide member with taking chess as a 'career' is strange to say the least.
Why there are so many chess professionals?

there are too many lawyers, bakers, doctors ...
Useful professions. ¿ What about chess? Chess is a funny game, people like funny things and becuase of that there are many profesional players.

lol, hardly any of them will be full time professional chess players. Only the top handful will make all their money from competitions. Some are partly supported by chess federations which are often government funded as chess is seen as a prestige game in some countries. For you to equate being a Fide member with taking chess as a 'career' is strange to say the least.
I already said in my post that not all the millions of registered players are chess professionals. But people who take chess as a career includes not only the players, but also non-participants like coaches, arbiters, tournament organizers, authors, etc
It isn't 'not all' it would be more hardly any of them would be classified as chess professionals. Many tournaments outside of the elite events don't have very high prize money either, many events are probably just organised by people who love the game than because they get money from it.
I wonder, why there are so many professional chess players in the world?
I think chess has more professionals than any other sport in the world or
perhaps more than professionals of all other sports combined together.
FIDE chess database has millions of registered players.
The FIDE database contains fewer than 200,000 players.
It's popular because it's the best game ever created , and it didn't derive from kicking peoples decaparated heads about like football

It isn't 'not all' it would be more hardly any of them would be classified as chess professionals. Many tournaments outside of the elite events don't have very high prize money either, many events are probably just organised by people who love the game than because they get money from it.
Thank you for your explanation.
I wonder, why there are so many professional chess players in the world?
I think chess has more professionals than any other sport in the world or
perhaps more than professionals of all other sports combined together.
FIDE chess database has millions of registered players. I agree, not all of
them are chess professionals.
Being a non-spectator sport chess attracts limited sponsorship only.
I don’t think, other than the supertournaments and world championship
cycle tournaments have decent prize money. Career in chess has limited
earning opportunity from non-participants. Also players have to spend
money from their own pocket for participation fee, travel fare,
accommodation, etc. Things that players encounter are
hyper-competition,financial problems, pitfalls, uncertainty, stress,etc.
If this be the case then why so many people take chess as their career?
Is it simply out of the love for the game or a way to avoid day job?