Particularly for those who are new to remote communication, it can be as trivial as not groking that this kind of interaction is just as real as face to face conversations. Just because you don't see the reactions doesn't mean that they're not there.
As we grow up, we're socialised with other people in the same space and you get trained to a kind of empathy. The patterns of interaction we reach by the time we're 17 aren't a default - if you spend time with people who were home-schooled you can detect that they evolve differently to kids schooled in the common form.
When we encounter remote communication, it's a new world. There's a much thinner feedback loop. Perhaps you usually use the other person's expression as a guide in your interaction, and then feel uncontained when it's missing. Without this constraint, a normally civil person become a monster.
Evidence that normal people become monsters is all around us:
1) Internet trolls, "I have an opinion. You aren't playing along. My opinion is sufficiently correct and the matter important enough that it's justified for me to grind you into the ground." And there's no tangible payback.
2) The way people talk in customer-to-business relationships, particularly where there is a difference in leverage and it's a one-off relationship. People in high leverage positions become accustomed to doing things without regard for the people they affect (e.g. insurance companies). It's common for people in low-leverage positions to become extremely aggressive in their conduct to try and compensate for a strategically poor position.
3) The way people drive. The driver sees themselves in a situation where they are competing for position. Subconsciously, "I don't care what you think because I'll never see you again." This is moderated somewhat by mandatory training, and by the risk of an accident which could create an embarassing and costly situation
4) Look at the way we behave towards animals we eat vs pets. The complex supply and investment chains are a machine that takes all kinds of humanity out of the field.
I've found a taste of distilled evil in the online version of the board game Diplomacy. The game is oriented around deception, with only minimal details of the other players.
I thought the handling of the matter excellent.
