No they won because they took a successful mod from a game and copied it
No, they actually hired the guys that made the mod to make it for Half-Life.
https://wiki.teamfortress.com/wiki/Team_Fortress
Because of its popularity, Team Fortress has spawned an endless amount of mods for not only Team Fortress, but other games as well. The game continues to be played competitively today, largely through its open-source fork FortressOne.
Valve took an interest in the Team Fortress Software organization and hired the three creators to work on a Team Fortress Half-Life mod, and later a standalone version called Team Fortress Classic (TFC), released in 1999. A standalone sequel to Team Fortress Classic, Team Fortress 2 (TF2) was developed by Valve and released in 2007.
Also it started with 2fort2
2fort4 and it wasn't the first map, but it was the most overused and overrated one.