Warning: Contains spoilers for Avengers #53
In Avengers #53, the past and motivations of Kid Thanos come to light, showing that this version of the Mad Titan is closer to the character's roots than the "main" Thanos that appeared in Marvel Comics for the past few years.
Kid Thanos was introduced in Avengers #50 as one of the members of the Multiversal Masters of Evil assembled by Doom Supreme and Mephisto to take over all Earths across the Multiverse. Not much was known about the character, besides the fact that he is a power-hungry lunatic who traveled to the past to conquer Earth, but was repelled by the Prehistoric Avengers. Even if young (by Eternal standards), he is a dangerous foe, as any version of Thanos should be. However, Avengers #50 - by Jason Aaron, Juan Frigeri, and David Curiel - gave readers a glimpse into his past, revealing horrific details.
Kid Thanos is presented more like a scientist than a warrior. He is fascinated by living creatures and, wanting to learn how they work, he disassembles them, just like clocks. Kid Thanos started with animals, then moved to his fellow Eternals of Titan, whom he considered "troglodytes" and "utter waste of carbon." After vivisecting four or five of them, he had a revelation: other living beings existed only for his edification, to elevate him to a higher state. This Thanos considers himself to be "in every fiber of my being - a scientist." He is obsessed with knowledge with what he describes as a "voracious hunger." This depiction of the character, while bone-chilling, is actually much closer to what Thanos was originally intended to be by his creator, Jim Starlin.
For the majority of his Marvel career, Thanos was surely a major villain, but one that could be more easily characterized as a mad scientist than a warrior. Most of his early exploit see Thanos busy with collecting mighty artifacts, such as the Cosmic Cube or the Infinity Gauntlet, but he does that not just for the power, but for the knowledge that comes with it. In fact, after his brief stint as a supreme being during the Infinity Gauntlet storyline, Thanos moves away from villainous activities for a while, and he is happily pursuing his true love, which is not Death, but rather knowledge (possibly of the forbidden kind). Most of the Thanos stories written by Starlin after the Infinity Trilogy present him as isolated, melancholic, and in search of the true purpose of his life.
This quest for a purpose is shared by Kid Thanos: the more he learns about the world around him (in gruesome ways), the more he wonders about himself. Finally, in his twisted psyche, it becomes clear that the answer to his questions can only lie in the place where he came from: inside his mother. That's why he murdered her, to open her up and look inside. It's psychotic, but it's also a much truer depiction of Thanos than what readers got used to over the past years. Thanks to the success of the movies Avengers: Infinity War and Avengers: Endgame, Thanos is more easily recognized as a warmongering conqueror, and the comics adapted to his depictions in the MCU. However, these are somewhat reductive, as there is much more to Thanos than that: a mad scientist, obsessed with the pursuit of pure knowledge to the point of forgoing any morals or ethics.
Thanos' gruesome murder of his mother has been introduced only recently in the continuity of the character (in 2019's Thanos Rising, by Jason Aaron, Simone Bianchi, and Simone Peruzzi). However, connecting the heinous act with his voracious hunger, Kid Thanos reminded readers of the roots of the character, and of how his true obsession was never for Death, but for something potentially more dangerous: knowledge.
Next: Thanos' New Attack Just Blew Up Marvel's Whole Timeline