The 25 "core"" sports for the 2020 Olympic Games are: athletics, rowing, badminton, basketball, boxing, canoeing, cycling, equestrian, fencing, football, gymnastics, weightlifting, handball, hockey, judo, aquatics, modern pentathlon, taekwondo, tennis, table tennis, shooting, archery, triathlon, sailing and volleyball.

It has been my opinion that Olympic sports somehow be related to combat activities.  Wrestling fits the bill precisely, as it can arguably be called, of all sports in which nobody shoots at you, the hardest.  A lot of other fit very well, some only arguably, while others require the battle experience of, well, the Swiss Navy.

Athletics: Most athletics (track and field) events pass this test.  "Run away to fight another day" explains most running events, and hurdles are just the hedgerows of northern France. The shot put, discus and hammer throws represent throwing heavy objects at opponents.  The pole vault is a little iffy.  A guy running at full speed with that pole in his hand pointed at  me would be a little scary, although I doubt one guy scaling a fortress wall in that manner made any lasting impressions unless the walls were higher than he thought.

Aquatics: Swimming makes sense as well, and in all styles, as one should use one's best method in the water to avoid an enemy.  Diving was vindicated in 1969 in "Butch Cassidy and the Sundance Kid," even if they did just jump.  Synchronized swimming poses a problem.  Fire an arrow at an angle an one is bound to hit one of them.

Fencing is fine, as is weightlifting as that is needed to move siege equipment and the like.  Archery passes without question, and in a combat context so does shooting.  The martial arts have their place, and judo and taekwando, although just creating a new name for an existing one after donning a feline costume and inserting plastic vampire teeth should not allow it to be considered separate from others.  They could be lumped into one "core," though.

Boxing certainly passes muster, and hence wrestling has to as, unless in a ring with a referee, most fights end up on the ground at some point or another.

Gymnastics has to be given credence for two reasons: 1) it was on of the first ancient Olympic sports and 2) gymnastics overseers through the years have devised some ridiculously hard things to do which entail a balance of strength, flexibility and balance. 

But now we arrive at the rest of the sports.  Any sport with a ball has to have a lot of worldwide popularity or some friends on the IOC.  Basketball, soccer, volleyball, and tennis have worldwide popularity.  Ping pong and badminton do also, if one primarily counts the Chinese, and if only from a population standpoint, that is "worldwide."  (Badminton actually utilizes a "birdie," leading one to wonder why "snipe hunting" has been ignored.)  Cycling is at least something most people have done, but the Tour de France is enough.

Rowing and sailing?  Sure, the two could be compared to elements of warfare - in a D-Day invasion scenario.  Why not lump these two into aquatics?  Equestrian is derived from chariot racing, albeit much like "Indiana Jones and the Crystal Skull" was derived from "Raiders of the Lost Ark" (with apparently a similar amount of time passing between them).    But handball and field hockey?  Those two I really cannot figure out.

Then there is the sport named after the most unrecognized Greek hero, Triatheles.  In 405 AD, after swimming the Aegean Sea, pushing a scooter until it broke, he ran he died, just shorts of Athens.  Hence Athens had no knowledge that the Spartan Admiral Lysander had taken the city of Aigospotamoi, leading to the siege and eventual surrender of the Athenian city-state.

OK- the first triathlon was held in 1974 outside of San Diego, California.  But this sport allows an "easy fix."  One of the "core" sports is aquatics, which, in itself consists of 34 events.  Another is sailing.  Why not just add sailing to aquatics to reach that "magic number" of 25?  Or split triathlon into it's three primary sports: "tri" into cycling (tricycle), "ath" into aquatics (bath) and "lon" into athletics ("The Loneliness of the Long-distance Runner").  (As if athletics would even know another event was added as it already awards medals in 47 of them.)

And that leave the modern pentathlon. 

The following may be found in the Encyclopedia Britannica On-line Website: