I was dating a guy for almost 2 months. The first month was great, we talked for hours on the phone every night.
He asked me to be his girlfriend on our first date, a month after matching online.
We had chemistry and our dates were between 26-48 hours long with daily calls in between.
One day, he comes over for a date, acts like normal (i.e. affectionate and kissy) and then when I bring up that he’s been distant the past week, he breaks up with me. What the hell happened?
There are a number of red flags here.
He asked you to commit to him after one in-person date - In a situation such as this, you must ask yourself why someone would be this eager to get you to commit this soon. While there's always a case that he just knew what he wanted and went for it, other signs you've discussed give me pause. Starting with...
Marathon dates - I've never been a fan of marathon dates. These are dates that last atypically long, even several hours. What tends to happen is a false sense of intimacy is built, which can affect a person's judgement. Marathon dates are a also a sly way to jam multiple dates into one night to expedite physical intimacy.
Lack of emotional self-regulation - That your minor criticism of how distant he seemed resulted in a complete 180 degree change in his attitude is very concerning. An inability to emotionally self-regulate is a common by-product of trauma. That could range from extreme criticism to physical abuse. His reaction to criticism should not be taken lightly. It could be a flash-forward of a very psychologically abusive relationship.
As I've said before, many people rush into a relationship in order to hide other - more concerning - personality flaws. It sounds like that could be what's happening here.
Nobody enjoys being criticized, but hearing constructive criticism and implementing change is one tenet of a healthy relationship. If he's not capable of that, better to know now than further down the road.