OK, well then your situation is different from OPs?

Because he doesn't seem to feel like there have been any explicit conversations.

Your comment didn't indicate at all that you had these explicit conversations. you had two sentences about your conversations with your ex:

He literally said that if I wasn't visibly angry or upset, he didn't realize what I was saying was important.

...

It really hurt to find out that by default he considered everything I said to be unimportant and not worth his time/attention.

and then you gave your advice:

Sounds like your wife has been trying to tell you how much she's been hurting for a long time.

we have no clue. the dude is sitting here, earnestly scratching his head wondering what the hell happened. It sucks that you had an asshole ex-boyfriend, but obviously there was a huge breakdown in communication between OP & his wife, right??

I mean, the dude is asking us wtf is going on in his marriage ... why his wife just up & left. a marriage isn't the same as dating, at least as far as I'm concerned. a marriage is a significantly bigger commitment.

that means that you work your ass off to communicate your needs & issues to your partner ... in a way they understand.

if they don't understand how you communicate, then you don't go and marry them. they dated for FOUR YEARS... and just 7 months after they got married, she bounced.

has he made mistakes? sure! but perhaps she could've communicated better. it doesn't matter anyway: marriage is a team sport, both are equally at / not at fault (again, fault is meaningless so long as they aren't wanting to divorce ... and even then, in most states)

the point is: they are having a communication breakdown, there's no need to declare that he is some clueless dude who just didn't listen to his wife.

if you clearly and explicitly told your ex the issues you had and he just casually ignored them ... then I'm not sure he & OP are the same person.