system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Was death of Odin the real cause why Thanos finally decided to actively look for Infinity Stones?
gpt
No, despite being a popular fan theory there is nothing in-universe to confirm that Thanos was waiting for Odin, Ego, and/or the Ancient One to die first.  All three of them were still alive when Thanos sent Loki and his army after the Tesseract in 2012 (at which point he already possessed the Mind Stone) and in 2014 when he sent Ronan after the Power Stone.

However, he did wait to openly and personally go after the Stones until he knew where all six were (or rather five and a person he knew well who knew where to find the sixth).  If all six were revealed and Odin was still alive, Thanos could probably have taken him seeing as Odin was severely weakened by the dark magic he used to send Thor to Earth against Loki's invasion.