I don't think the WSSMs would have been a success even with a 1-8 twist in the .223. There were several other problems.
Their big problem was their shape/head-size requiring entirely new bolt-actions from both Browning and Winchester. One thing that definitely helps newly introduced cartridges (which often mostly appeal to real rifle loonies) become establsihed is being able to rebarrel existing actions to the new round. This was difficult with the WSSMs, since they were both so fat AND short.
Plus, while the .223 produced faster velocities than the .22-250 and .220 Swift, the velocities of the .243 and .25 WSSms didn't improve on already existing rounds. I know quite a few rifle loonies, and only two purchased .25 WSSMs--and one of those was a fellow gun writer who got his at a discount. Never ran into anybody who owned a .243 WSSM, perhaps because even then the trend was to 1-8 twists in 6mms, and like the .223 the factory twist was 1-10.
Of course, Winchester shutting down didn't help, but the WSMs survived the hiatus in production. As noted in an earlier post I purchased a new Model 70 in .300 WSM in 2008, and three of the four original WSMs (all except the 7mm) are still chambered in Browning and Winchester rifles, and the .300 WSM is regularly chambered a bunch of other American-made rifles, as well as by European companies including Blaser, Sako and Tikka.
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