system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] How did Titan die?

First of all, I’m sorry if this question has been asked before but I’m not very active on the sub so I don’t know some posts. If this has been asked before, then could someone please link to me to the post, thanks. Also, sorry for formatting, I typed this on my phone. 

Alright, so Thanos claims that overpopulation destroyed his planet. Apparently the problem was so bad that he appears to be the only survivor and his planet seems have been completely abandoned and desolate. But I just don’t understand how overpopulation could destroy a planet like Titan which (I’m assuming) had at least some knowledge and interaction with the galactic community (considering Thanos left to conquer that community after his people died) and apparently didn’t benefit from those interactions enough to stop a problem that oil-powered human civilisation has today. 
I mean, obviously Thanos’ solution to snap Titan was stupid, but did nobody offer a better solution? Did they never colonise another world, build superstructures for housing, heck, even freeze their people for future awakening? 

The MCU is a world where a rainbow bridge can take one from pretty much anywhere to pretty much anywhere, where godly beings like Celestials exist (or at least existed), where neutron stars can be reignited by a dwarf, a raccoon, and a god, etc. In this crazy universe, Thanos says that *overpopulation* us still a problem?? 
That’s not even getting into the issue of the gravity thing. How did Titan’s gravity get weird? Overpopulation? Or was it that the gravity issue is what destroyed the planet? I feel like it was the gravity problem that caused the demise of Titan, and that Thanos is lying about the overpopulation problem, but that just feels wrong. It would undermine Thanos’ whole motivation and make him unsympathetic. 

So, what killed Titan? Was it overpopulation? The gravity thing? If it was overpopulation, how?
gpt
Titan may have been a spacefaring civilization, but it might not have developed interstellar travel yet.  Ecological disaster is gonna get you, if the only places you have to go are nearby barren rocks.

Which leads me to overpopulation.  Too many people, consuming too many non-replenishable resources, can kill a planet.  Climate change from things like depletion of ozone layer and too much CO2 in the atmosphere released from a technological civilization can cause a runaway effect.  It frees up more greenhouse gasses trapped in permafrost or tied up in biotic systems, like marine plankton.  

As the world warms, more warming agents are released, creating an ever-increasing positive feedback loop.  The end of that road is the collapse of most food webs and most life.  The people that depend on that life, which is everyone, then die off themselves.

The gravity problems may be due to Titan's particular brand of technology.  Those big jack-shaped things in the sky seem to stay aloft due to some manipulation of gravity.  That may have been part or all of the problem too - overuse of anti-gravity leading to global destruction.