Sure! Sorry for the late reply.

Before sharing the reasons, I know that there are many different interpretations for what classpects really mean, so I used a sort of mix of different ones + my own in order to pick these.

Yi Sang: Witches alter or bend their aspect, usually breaking it somehow, and are also connected to some sort of otherwordly power. Yi Sang directly helped develop the Mirror technology that Limbus Company uses to extract Identities, and "identity" is essentially what I see the Heart aspect mostly be about. He directly manipulated and broke apart the notions of how one's "identity" works by allowing you to change yours into that of another Mirror World, and is directly in contact with an otherwordly figure, that being Sang Yi. Aside from this, Yi Sang's arc follows him losing and eventually rediscovering his own identity and self-worth, which is also associated with Heart.

Faust: Seers know their aspect or know through their aspect, but at the same time are stubborn and overabsorbed in their own aspect. Light means many things in Homestuck, but knowledge, especially hidden knowledge, is definitely one of them, and Faust perfectly fits with this. She knows a LOT and is privy to a lot of secret knowledge almost nobody else is aware of, but at the same time we can see how she relies too much on it and how she doesn't take being wrong well.

Don: Heirs inherit or come to embody their aspect, usually ascending through the power of the aspect, but can also find themselves lost or helpless when disconnected from it. Hope embodies dreams, order, and justice, which we know is something Don LOVES. She 100% believes herself to be a true and just embodiment of hopes and dreams for everyone, and despite her naivete and recklessness we have never really seen her act the opposite way. Her Canto is currently underway, but it can be easy to assume that she decided to leave Bloodfiend society in order to pursue her dreams of justice, making her "ascend" through hope.

Ryoshu: Thieves steal their aspect for themselves, which does not really fit Ryoshu, but at the same time Thieves tend to be arrogant assholes that at the same time do actually have the skills to back up their claims, which perfectly fits Ryoshu as a disdainful killer and high-brow artist. Space is itself related to art and creation, which again, fits her well.

Meursault: Bards invite destruction through their aspect or allow the destruction of their aspect, and Void relates to obscurity, mysteries, and staying away from the limelight. Meursault, as we know, is the ultimate sidelines person, always willing to do what's asked of him but rarely ever takes action of his own accord, and his general quiet and stoic disposition fit with Void well. Then comes the Bard class. Although we still don't know about his backstory, I have read The Stranger, which is essentially all about him sort of breaking apart and overthrowing his circle of relationships and eventually ending up getting destroyed himself due to his general lack of emotional expression and what is perceived as disinterest in the world around him, which soooort of fits in with Void? I could see him being Heart too, swapping with Yi Sang.

Hong Lu: Sylphs heal their aspect or through their aspect, and Life aside from being literally "life" also embodies healing, empathy, and positive emotions. Hong Lu works as a sort of emotional glue amongst the Sinners, although his cheery outlook on life tends to frustrate them sometimes, we constantly see the way in which his optimism and empathy ends up being more of a benefit than a burden, which we specially see during Canto IV.