Interstellar #2 - What happened with "Mann"

First of the two major points that stood out for me in the movie.

Dr. Mann has faked the data he found on the new icy planet and lured endurance and its scientists to land there. When he learns that cooper would be leaving the planet on his shuttle to get back to earth he takes him to a lonely spot and tries to kill him, while talking about how humans have not "yet" evolved enough to put the importance of surviving as a species above saving loved ones (which, in this context, borders on selfish). This emphasizes the fact that humans are the youngest species on the universe (meaning, if there were other species on the universe, aliens, they, as a species, would be more evolved as they've been alive for a longer period than humans). So, the "beings" mentioned every now and then can either be taken for God and Angels or as an alien race which wants to see humans grow and evolve by helping them survive.

Mann portrays the raw human nature which portrays man as being rash and selfish (when he talks about success of the mission and ultimately his glory on achieving it) but still wants to leave his cohorts behind and get out of the icy planet. while cooper is struggling to breathe through the ammonia in the atmosphere, Mann experiences an inner conflict which being human, wants to save his new friend and being a scientist wants not to jeopardize the mission. I imagine scientists going through this conflict every now and then, growing up believing something only to learn and realize that their belief system "could be" wrong. the key word here is "could be" because the biggest, life altering theories one can learn are just that, theories and not hard facts, not yet.

Sso why is the planet so icy. If u want it to be un-inhabitable u could've made it rocky with no water, an atmosphere rich with toxic gases, surface that can explode anytime, I don't know a hundred possible scenarios? and you choose ice. I believe ice shows the cold, unforgiving and non-compassionate nature of humans when it comes to putting their self before others. There's another possible explanation. Americans in general don't like the cold, they prefer warm, sunny days over the cold ones. Is that why an uninhabitable planet came to be an icy surface with frozen clouds and a final settlement camp of humans looks warm and cozy?