Thanos has everything you want from a supervillain: a compelling backstory, a mission that makes sense to him despite causing worldwide devastation, and even a soft side as an adoptive father. (Not that his daughters would necessarily see it that way...)
But one of Thano’s most underrated qualities is his ability to manipulate others to get what he wants, all while hiding his true intentions. This theory suggests the Avengers villain used these skills to build the Infinity Gauntlet, as early as Phase 1 of the Marvel Cinematic Universe.
Heading into The Avengers, Thanos loaned Loki the Mind Stone to conquer Earth in return for the Tesseract. But why would Thanos need Loki to get the Space Stone? He’s more than capable of invading Earth as we see later in Infinity War. He doesn’t need to outsource the work to Loki...
...unless he had another use for him.
Tricking the Trickster — Loki may be an unpredictable trickster demigod, but one thing about him is always consistent. He will always be a corrupt agent of chaos. Thanos knows this, and he also knows the only place suitable to create a containment device for these ultra-powerful stones is Nidavellir, the dwarven world under the protection of the Asgardians.
So Thanos enlisted Loki to not only help him get the Space Stone, but to further corrupt him as a supervillain. This would cause unrest in the Asgardian royal family, creating enough instability so the Mad Titan could simply swoop into Nidavellir, force Eitri to forge the Infinity Gauntlet, and then destroy the forge and the dwarves so the Avengers can’t create something that could stop him.
Of course, if this was Thanos’ plan, it didn’t exactly work, as Thor, Rocket, and Groot were able to forge the Stormbreaker — but hey! It’s the thought that counts!
The Inverse Analysis — Was Thanos really ten steps ahead throughout his whole run in the MCU? The idea certainly has some holes in it.
Why would Thanos risk both the Mind Stone and the possibility of getting the Space Stone for this very, very, long-term plan? The stones aren’t worth anything to him until he has a way to use them, so risking anything in order to get the Gauntlet forged and working might have been worth it to him. If Loki fails, he could just invade Earth and get the stones on his own.
Regardless, Thanos definitely allowed Loki to play into his schemes for a reason — whether that reason was causing secret political unrest, or the sheer convenience of lending one stone with the hope of getting two.