MCU: 14 Things You Learn Rewatching The Avengers
11. Thanos Giving Away An Infinity Stone Will NEVER Make Sense
No matter how Infinity War deals with Thanos giving Loki the Mind Stone in the shape of the sceptre, it is never going to look like a huge mistake.
Even if it turns out he knew the Stone was inside the artifact and he was gambling on the chance to get the Tesseract AND the Mind Stone based on Loki's deceptive assessment of humanity as a push-over, it still makes Thanos look silly.
He was needlessly careless with something he was supposedly dedicated to finding and no amount of Loki's help could justify that. And The Other explicitly says that his agenda - and presumably Thanos' - is to access other worlds greater than Earth. That's not why he wanted it at all, according to his retconned story that emerges later, so it's clearly a story-telling oversight that Loki gets an Infinity Stone.