AlienWarlord
There must be plenty of reasons why Thanos chose that route, not that the actual writters and staff of the movies knew, but, some reasons can conveniently fall in place by coincidence. Like by increasing the ammount of worlds also will make civilizations want to expand, and now without a natural barrier of plenty of dead planets creating a sort of barrier and border between then, they will probably have many more conflicts between each. Dead beings and beings that "shouldn't be born" now can pop more often now that their nest/prison is more lively. Not to mention beings like Galactus and etc. BUT that is only because of the limitations of Thanos, and he proably wouldnt be able to deal with all the issues that surged with another path, he wouldn't have the power to deal with the new threats, so he was locked into that option, but Peter might have the power to do deal with all the new issues, having the otion to pick a more benevolent path.