We got none of that. What we got was Thanos rambling and a screen shot from a completely untrustworthy narrator.
If we are saying Thanos was untrustworthy when he was talking about Titan, then we don't have much to go by in terms of character. In my mind, much of his motivation comes from that scene. I personally enjoy the character, and thought it was well handled.
From his little speech I was able to gather that his planet was overpopulated, that he offered an, again, crazy solution that actually probably would have helped... and ultimately the harsher reality came to pass. He probably feels vindicated based on Titan, but has lost his ability to approach this rationally. The reason being his experience dealing with critics when he actually had a plan that was more based on the problem at hand and likely dealing with the traumatic, emotional experience of seeing people he knew pass away under probably horrible circumstances (if the problem was lack of resources, I imagine a lot of infighting). I felt this trauma is often overlooked, although expressed in a single line:
Thanos: They called me a madman. And what I predicted came to pass.
Doctor Strange: [sarcastically] Congratulations. You're a prophet.
Thanos: I'm a survivor.