Short answers, pulled from the story.
The original Dungeons and Dragons box set had a production budget of only $2,000 to print a thousand copies. Just $100 of that was allocated to artwork, and artists were paid $2 for small pieces and $3 for larger ones.
In 1977 TSR published both the Basic Set, an introductory version edited by John Eric Holmes, and Advanced Dungeons and Dragons, a reorganized and expanded ruleset compiled by Gary Gygax. The Basic Set was intended to funnel new players toward AD&D after third level, but in practice the two games developed distinct fanbases and continued in parallel until 2000.
Advanced Dungeons and Dragons 2nd Edition was published in 1989 after a team led by David "Zeb" Cook began work in 1987. Major changes included the removal of demons and devils by name, the elimination of the assassin and half-orc as character classes, a shift toward heroic roleplaying, and replacing the Monster Manual with a loose-leaf Monstrous Compendium.
The Open Game License (OGL) was introduced with the 3rd edition in 2000 and allowed other publishers to create compatible content using the d20 System without needing approval from Wizards of the Coast. It enabled Pathfinder by Paizo Publishing and a movement of retro-clones including Labyrinth Lord, OSRIC, and Swords and Wizardry.
The 4th edition, released in June 2008, overhauled the game into a tactical combat system requiring miniatures, standardized character class powers, and extended core rules to level 30. Many players found the changes too dramatic and migrated to Pathfinder by Paizo Publishing, itself based on D&D v.3.5, which became one of the best-selling role-playing games in the industry.
Public playtesting for the 5th edition began on the 24th of May, 2012. The 2022 playtest for the subsequent revision attracted more sign-ups since its August 2022 launch alone than the entire two-year 5th edition playtest had seen before the game's 2014 release.