As of writing this, Lego Lord of the Rings and Lego The Hobbit have been removed from sale on the steam store with no word or reason of why from publisher Warner Brothers. They did have this to say,
The game originally disappeared from Steam, PlayStation and Xbox stores on or around 1st January – suggesting some kind of licensing restriction ran out at the end of last year. This come has a shock to people who enjoy the Lego games, the two removed being a few of the fan favorites. Lego Lord of the Rings introduced a fun Open World. In the open world mode of the game, the player controls 2 changeable characters and is allowed to freely explore the game world, which spans the entire world of Middle-Earth minus Mirkwood and the lands south of Mordor. While players primarily travel on foot, they have the option of using Fast Travel through the Map, which transports the player to any location they’ve been to and allows the player to change the time of day. They also have the option to ride horses at specific locations throughout the game world. Lego the Hobbit had its own crafting tree, making it unique Hopefully a deal can be made to bring the games back on sale at a later point.
Luckily, if you already own the game you’re fine for now. The games shouldn’t disappear from anyone’s library, so play the game while you can! Hopefully, it stays this way. The Humble Store gave the games away free in December, and I guess now we know more about why. Steam and Humble had them heavily discounted in the run-up to the vanishing too. But if you missed out, you’ll need to search around other stores for boxed copies or Steam keys. They are still out there, but supplies do now seem limited.