<p>The primary reason for why Thanos has this mindset is because of what happened to his home Planet: Titan. As he explained in Infinity War. His race were people who could live a very long time, but kept reproducing irresponsibly. When the threat of civilization collapse was immanent for Titan because of this. Thanos proposed genocide to half of the titans to save their planet. But his kind rejected him.</p><p>
</p><p>They never tried to elaborate on how this could have made things worse for Titan, nor why it should have been condemned and thus change Thanos' thinking style for this. When TItian fell and Thanos became the only survivor, from it. His voice and reason was the only one left and thus he became cemented in his belief that his solution would have saved Titan. Which gave birth to his ambition to spread it across the universe.</p><p>
</p><p>In Thanos' mind, it works. Infinity War tried to show justification of the results of his actions on other worlds like he described the effects he did to Gamora's planet as "a paradise" .</p><p>
</p><p>Thanos's reason for this is based entirely on what Titan had to offer. If that planet had the ability to double resources, then he could have tried to spread this across the universe instead. But the fact that they didn't and his mind has already been cemented on the genocide method. He would never try to double resources as a solution.</p>