Mario is par for the course for video game protagonists - saving the world, one corpse at a time. "Heroes" let nothing, certainly not the lives of living creatures, get in the way of their mission. These creatures are transformed into "monsters" in order to ease the conscience of the "hero" who casually removes them from existence if they are any kind of obstacle between him and his goal or if they offer loot and XP - if their deaths grant the "hero" even a slight amount of additional power.
This goes back to Dungeons and Dragons, where the "band of heroes" go out of their way to enter dungeons, the home for living creatures whose crime is being too ugly (in the eyes of humans) to show themselves on the surface of the world. Because these creatures have already been demonized, pushed out of civilization, and forced to live in dank caves or under the earth, it's easy to simply call them "monsters" and exterminate them, in order to make the "heroes" rich and improve their killing ability, thus allowing them to kill richer and more powerful "monsters". Take careful note that these "monsters" get along with EACH OTHER just fine - the "heroes" never enter a dungeon just to find that the "monsters" have already slaughtered each other - they always enter to find a community of creatures living happily or at least tolerantly with each other, and a "successful" result for the "heroes" is always genocide of the actual inhabitants of the dungeon by raiders who leave only rotting corpses behind.
The idea behind all of this is cleansing the world of evil, but it's ASSUMED that the creatures being killed are evil - if they were actually evil wouldn't they be killing *each other*? How can these biological creatures who require sexual reproduction to come into existence, who require nurturance and care to grow and learn about the world, who then form a community and work with others to maintain and build that community, and who only "dislike humans" because those very humans have demonized and excluded them from "civilization" be considered EVIL?
Then we come to the real reason they are considered evil, the same reason the Native Americans were considered "savages" while they possessed wealth - in order to JUSTIFY the taking of the wealth. The "band of heroes", the Fighter, Thief, Magic-User, and Cleric, their civilization having excluded and marginalized the ugly creatures of the world, pushing them into caves and dungeons, then implement the Final Solution of genocide and theft, similar to how the Jews in Nazi Germany were pushed into ghettos and then exterminated.
The extermination of the Native Americans was a lot better than Dungeons and Dragons, because at least the European invaders actually use the land they stole. The "band of heroes" doesn't give a shit about the land the "monsters" live on - they leave immediately after the slaughter to return to their own community, never to return. It would be like if the European invaders came to North America, killed all the Natives, stole their material possessions, and then returned to Europe. At least there would be *some* justification for a D&D slaughter if there was mass overcrowding on the surface and this forced people into areas they had previously refused to live in.
It's funny, but not in a good way, that we criticize "greedy, power-hungry" people like dictators and corporate moguls but then we engage in a "for fun" activity of mass genocide, theft, and "leveling up" to allow us to kill stronger and stronger and richer and richer "monsters".
The serious question remains unanswered through all the decades since Dungeons and Dragons was born - why is the mass genocide and theft of marginalized creatures for the empowerment of members of the dominant society fun? Why does this mass genocide and theft happen to be preferred by wealthy Westerners, mostly men, many of whom happen to be living on stolen land following a mass genocide?
Why is that the PRECISE type of fun that we enjoy? Why is genocide so enjoyable as long as it involves merely virtual creatures?
"It's just a game". Sure, but we could be playing ANY game or not playing a game at all - so why do 61% of mainstream games feature killing as a primary form of gameplay, most involving marginalized or dehumanized people as victims with the "hero" becoming more powerful with every kill?
Think about this on a basic level. Let's say you meet a typical video game protagonist. Whether you live or die is determined largely by whether or not you're labeled as a "NPC" (a fellow civilized creature) or a "monster" (someone excluded from "civilization"). Once you're deemed a "monster", then your only hope for temporary survival is being more powerful than the "hero" and thus unable to be killed, and since you're a good person you foolishly don't kill the hero, or maybe you're wise and try to kill the hero only to have the player possessing him use his Reload Function to cheat death, which he then follows up by becoming more powerful and returning to kill you.
What's generating this experience? What's the motivating factor for why we play the games we do?