Charisma is not a dump stat and in fact its just the opposite.
From my reading, older D&D (OD&D and AD&D with elements in 2nd edition here) assumed the characters had a retinue of henchmen and hirelings and would care for and equip them like Housecarls . Its why so many of the old modules had extra magic items. Its a gift economy.
Some of them you'd keep for yourself , a few you'd trade or sell and some you'd gift to your henchmen . of course some some you'd never find at all.
In those terms, the number of items was well suited to the party size which instead of the 4- 5 A-Team we assume now band was a War Band, 5-8 PC's with their own henchmen. hirelings and sometimes war animals.
At "name" level this situation was formalized with an actual War Band with numbers the hundreds for fighters and dozens for others.
The thing is as I understand it anyway those leaders were in addition to henchmen as they were attracted to the characters in world power and prestige.
This meant 9th level Lords (Fighters) say were serious power players able to field several men capable individually of killing an ogre and a small army of men at arms as well.
As such the higher the charisma, the better people reacted to you and the better you did in the end game
Now, yes later classes that weren't endgame focused did come, The Paladin and Ranger to a degree being the big examples about but remember the original 3 (Fighter, MU, Cleric) all had followers and the later add on Thief did as well.
Lastly, D&D has always had a social option and reaction rolls and unless the characters are all murderous vagabonds, at least a few people in the party need the charisma and social skills to talk to people
As such, Charisma was not a dump stat.