...Even tho they had the same pickups, the slimmer and lighter SGs were far outselling the older LPs....
The real reason the SG outsold the LP was its low price. The SG, Gibson's "Fender Fighter", was priced to match the Fender Stratocaster which was half the price of the Les Paul. "That Fender guy with his slapped together planks" was beating sales off Gibson's LP by a wide margin and they were frightened. The cobbled together SG design gave players humbuckers to cut noise over the Fender single coils -- a performance enhancement to sweeten the deal. Of course the SG sold more than the LP. Gibson could have priced the LP the same as the Strat and Tele and sold those like crazy too, but the LP was built with a lot of waste (a standard board length gives an even number of Tele bodies, while the same board leaves a wasted half to two thirds of an LP body).
All the famous guitars became famous because the model was out of favor when found cheap in pawn shops the world around by players with no money who would one day be famous, dragging their guitar with them up the charts. These days of average to pro players having a fleet of guitars never get associated with any particular model like the old days:
LPs: Zeppelin and The Who
SGs: ACDC and The Who
Strats: Hendrix and Clapton (then later EVH's FrankenStrat was put together from scrap non-Fender parts, rattle can painted and relic'd ... and almost put Gibson and Fender out of business)
Teles: Many ... Indie and punk bands found them when still associated with Old Country.
Jazzmasters: J Mascis (he didn't have money for the Strat at the music store, but did for the unwanted Jazzmaster)
There was a behind the scenes video on youtube where Gibson gave Elvis an SG to play in some surf movie he was doing at the time. You can see Elvis' face reveal his immediate opinion "this is not a guitar anyone wants to be playing". He played it because that was the deal Gibson made with the movie producers. But that look on his face was telling.
Price of a guitar new and later pawn-shop-used will set the stage for future fame of that guitar.