Titles of standalone literary works are generally not trademarkable. You need to have a series (Harry Potter) or significant commercial tie-ins (Spaceballs: The Lunchbox) to pull it off.
King's "Saga" games do not appear to be a series so much as an attempt at a branding umbrella. That's much weaker than "Elder Scrolls", which is a series with common elements. Just "Scrolls" by itself is a long stretch, as the company did not produce other series with that word in it, like perhaps "Younger Scrolls" or "Forbidden Scrolls" or anything other than "Elder Scrolls", so confusion with "Magnetic Scrolls" was very unlikely.
Again, as software falls largely under copyright, I don't think King has a leg to stand on from legal tradition. But our courts don't necessarily do what we think they should, either.