system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] Exactly how was Thanos able to amass such a large, if not the largest, force without any kind of coalition coming together to stop him at a weaker point?

Thanos didn't amass this force overnight, I'm assuming. How was he able to band together such a large army without showing his blatant warmongering off to every planet in the nearby galaxy? Did no one try to stop his growing power?
gpt
Thanos started off as not only a genius, but also as the last survivor of his entire race. 

Leave Tony Stark alone on Earth for a couple of years, and with access to advanced alien technology, and he's going to leave pretty powerful.

We never really get told what the non-human things in Thanos's army are. Maybe he actually created them using advanced bio-engineering, once he had the resources of an entire planet/advanced civilization to himself?