After mysteriously vanishing in 2019, both Lego: Lord of the Rings and Lego: The Hobbit have returned to Steam, as noticed by Reddit user knightpowell.
Sometime in January 2019, both Lord of the Rings games were quietly removed from Steam— as well as Xbox 360 and PS3— without any warning or announcement as to why it was happening. Since then there's been no word, until recently when Lego: Lord of the Rings and Lego: The Hobbit appeared back on Steam as mysteriously as they left it.
Even if there's no official reason for the games' absences, it's not hard to make a guess. Both titles must require a large number of licenses between Lego, Lord of the Rings, and all of the other toys and rights-holders with a stake in either franchise; it's possible (and likely) that they were removed over a licensing issue. Other Lord of the Rings games including Middle-Earth: Shadow of Mordor and Shadow of War were not removed, so perhaps there was an issue on the Lego side of things.
Lego: Lord of the Rings and Lego: The Hobbit are both based on director Peter Jackson's film adaptations of J.R.R. Tolkien's work, albeit taking a considerably lighter approach to storytelling as all Lego titles do. It's not clear at this time if the games are also available for Xbox 360 and PS3 once again.
Lego: Lord of the Rings and Lego: The Hobbit are available for PC via Steam.
Source: Reddit