Though you have to agree, you were near it but had reconciled, maybe even didn't involve lawyers. They on the other hand divorced and official divorces are usually quite messy, especially if one of the partners worked more.
As for their situation it's too vague, he is working long hours especially in Japan it isn't news. If their conflict started simply because of his long hours, i presume they already had conversation about this issue. Also by the looks of it despite him busting his ass she accused him of cheating without any base (in real world it can actually mean the opposite the accuser is cheating, especially if you didn't cheat nor given any suspicions).
Next point, many marriages are going through divorce exactly because of financial reasons (young people who don't have children and are not established OR established families when one of the partner can get a jackpot by divorcing). Young couples divorce usually due to women finding more perspective partners and our century add-on better perspectives(job), as for old couples it's once again usually women who fell out of love, grew tired and see NET benefit by taking 50% and living free. (Based on stats that majority of divorces are initiated by women and majority of reasons are financial, i excluded
irreconcilable differences due to them being just an umbrella term for real causes : finances and cheating).
Irrationality is indeed seen in their conflicts but there is also some sound logic, if you bust deadly hours at work and come back home only to get chewed and drilled, you would also quickly fall out of love and want a divorce. Btw completely not gendered accusation, if the roles would be divorced i would have the same concerns.
For example real life situations both work until 5, get back, he plays games and does his stuff while "mommy" cooks and cleans, if a wife/gf would be pissed with this i understand even if he has hard manual labor job(sadly we cannot count how much someone loses real energy), if after some talking common ground cannot be found, divorce is only option .
Other situation from real life experience, husband works 50-60 hours a week, wife does a part time 20h at best, she demands his participation in cooking, cleaning and laundry. Conventional male jobs are on him of course.
My point is mangaka once again hides the full story (probably) why they divorced. If it's really, because of his work, i blame FMC if there were some tangible offenses from him situation might change. The problem as usual, mangaka has a stupid idea, he creates it but doesn't close all the loose ends and during the course of new volumes does some first aid to the story until it collapses under it's illogical, demining and ridden with plot holes balloon. Just speaking from experience that when i busted my ass 50-60 hours doing physical job with toxic elements to boot, if someone would bark at me after that job, i would snap quite fast.
P.S. Happy for you that you kept your marriage, wish you the next decades of happy marriage.
