To be honest, Thanos understood Robet fairly well. After all, he had already used the Mind Stone to successfully control Thor, and from Thor he had obtained quite a bit of intelligence about Earth—the most crucial of which was information on Robet.
Because of the distribution of the Infinity Stones, Thanos had long wanted to make a move on Earth. But Earth was no ordinary place. Leaving aside Odin, the old All-Father of Asgard who had once protected Earth, even Earth's guardian, the Sorcerer Supreme Ancient One, was not someone Thanos was fully confident he could defeat.
Especially at the very beginning, when the stone in Thanos's possession was the Mind Stone. Even with the Infinity Gauntlet, Thanos did not believe the Mind Stone could easily control the will of a Sorcerer Supreme and turn her into his slave—much less when Ancient One also had the Time Stone in her hands and commanded the corresponding time magic.
Because of that, Thanos had never been willing to do something so uncertain. Even after the All-Father Odin aged and Ancient One disappeared, Thanos still did not dare go to Earth personally. Instead, he sent his subordinates to test Earth's situation—and that test had nearly cost him the only Mind Stone he had.
In fact, for Thanos, this operation on Earth had truly been a heavy loss. Not only had he lost two members of the Black Order, the Chitauri army had also suffered grievously.
Although both sides relied on mass-produced biochemical troops, it was obvious that Thanos's Chitauri army could not compare to Darkseid's Parademon army, whether in numbers or reserves. The losses from the last Battle of New York had already badly weakened the Chitauri. After all, producing large numbers of biochemical soldiers also required resources...
It was precisely because his