That's part of the problem with all of this, the lack of options. Imagine being a decent and otherwise normal and functional individual but your only avenue to meet the opposite sex, whether you are a man or woman, is through old sites and apps. In the case of a man, imagine being totally average, which is made up of countless millions of individuals, and having little to no success with this. Imagine getting a handful of matches or responses, thoughts like "this may be the one" will begin to circle in your mind because of your lack of options. Now let's factor in experiencing a lot of time just messaging with nothing come it, or maybe last minute flakes or just getting a single date and then nothing......that is eventually going to have an effect on you, especially if you have no means of venting about your frustrations.
There are tons of people out there with no one to confide in when it comes to their personal issues that they face, which is not good for mental health. I guarantee you this guy is most likely not that bad of a person, he simply just was at a tipping point and this woman's behavior triggered him and set him off. It's really not difficult to see why and how stuff like this happens and I'm sure it's not all that uncommon, especially since COVID hit 2 years ago. I actually feel bad for a lot of men who otherwise don't know any better and have honestly no clue what to do.