Let's look at some of those gentlemen:
Abner Doubleday was a professional soldier, a Civil War general, and a pretty good one. He is lesser-known in that capacity because he wasn't in any of the famous battles, and was quiet and efficient. He MAY have played "town ball" as a youth, but his only real connection with the game as an adult was to suggest to his men that they organize teams and play each other to pass the time. (War time in the Civil war was about 3% time spent fighting and the rest either moving or idling. Commanders were constantly seeking ways to keep their men fit, healthy, and occupied. For Doubleday, baseball was among his ideas.)
Cap Anson...Great player, decent manager, yes...but he was a virulent racist, and was almost singlehandedly responsible for the unwritten ban against blacks in the major leagues.
King Kelly...While highly-popular for a few years,(Even had a song written about him, Slide, Kelly, Slide.) was a drunk and a swindler who loved to gamble, cheating when he could...but basically stayed broke. He died when, after he was thrown off a streetcar in Boston for being highly intoxicated, loud and vulgar, he tried to follow it across a bridge...and fell into the river.
It's doubtful that Kelly woulda had a long career or avoided prison today.
However, Kelly with Cap Anson developed many of the baseball plays still used today...the hit-n-run, various "squeeze plays" involving bunting, various double steals, and other base running tricks.
Wee Willie Keeler...Played a style similar to Kelly's, but was somewhat more organized and sober off the field than was Kelly...had a great sense of humor.
Once, on a train, his manager(Can't remember which one) was complaining they had the poorest accommodations on the whole train. Keeler said, "I can get us GREAT seats if you have the guts!" The manager said, "You know me..I've got the guts do do'most ANYTHING!" Keeler then donned a conductor's uniform he'd found in a locker & said, "Follow me!" Into a 1st-class car they went where Keeler announced that this car was gonna be disconnected at the next stop due to mechanical probs & that all passengers should move to other cars, which they did.(In those days, baseball players weren't as recognized out of uniform as they now are.) Keeler & the manager had a 1st-class car all to themselves. The manager said, "that was easy-Where do the guts come in?" Keeler just smiled & removed the uniform. The train passed through a town w/o stopping, & some of the displaced passengers began returning to the car. Keeler winked at the manager & said, "Here's where the guts come in".
He was 5'4", 140 lb at the most & used a tiny bat, 30" long, 29 oz. weight. But he was strong and very quick, and a very accurate batter who very often DID 'hit'em where they aint'. He is among the all-time leaders in fewest strikeouts for a career. His contribution to the game itself was his immense popularity as a player. He did not help develop the game otherwise; he merely carried out the hustling style of play developed by Anson and Kelly.
Candy Cummings...His nick came from the slang "the candy" for a superlative, much as "You da man" is used now. Even though a player named Fred Goldsmith claimed to have invented the curveball, Candy publicly demonstrated it by standing slightly to the left of a thin pole, from which a line had been drawn to another pole some feet away, and to a third pole somewhat further away, to show they were in line. The right-handed Cummings, while standing in line with all the poles, threw the ball just to the first pole's right, passing the second pole just to the right, and curving by the third pole on the left.
Cummings weighed only some 120 lbs in his playing days, and therefore was worn out as a player by age 27...but he often pitched both ends of a doubleheader and some 50-60 games a season. He was soon forgotten after his career was over, and he did nothing to keep memories of himself alive.
Remember, Cummings pitched in the era of underhand pitching and a 50' distance from mound to plate.
Cartwright was a major contributor. His rules quickly became the standard for most organized baseball at all levels. I shall post those rules in a separate post.
Cartwright was a businessman and a firefighter, and that came before baseball. He moved to Hawaii, where he organized the first Honolulu Fire Dept.
Henry Chadwick, an Englishman, was the greatest baseball writer of his day, perhaps for all time to now. His contributions to the development and popularity of baseball are as great as anyone who's ever lived. He developed all the stats now used, the modern box score, and the weekly baseball tabloid, the Sporting life. he also wrote several books to teach baseball techniques to new players.
That's all fer now, folks...