Williams played 12 snaps, all on the first drive (when the 49ers marched down the field for a touchdown). Deebo played 20 snaps (basically 2 drives). Aiyuk played 23 snaps. Bosa played 8 snaps. Fred Warner played 12 snaps. Not surprisingly, those guys all played during the portion of the game where it was lopsided in favor of the 49ers. The 49ers held the ball for 21 minutes in the first half while the Rams had it for 9, and the total yards were 274 to 108. Let's not pretend it was at all close when the 49ers had half of their good players playing.
(Armstead, Jennings, Kittle, and Greenlaw didn't play at all (in addition to CMC and Purdy), not to mention both starting safeties didn't play.)