UPDATE 4/1/19: It sounds like Lego Lord of the Rings and Lego The Hobbit's digital download versions have been removed from sale permanently.
Publisher Warner Bros. has not said why the games were delisted, but gave Eurogamer the following comment - confirming the games are no longer available to buy:
"Lego The Lord of the Rings and Lego The Hobbit will no longer be available for sale in digital stores," a WB spokesperson said. "The games will remain in players' libraries if they already own them."