I’d challenge the word “cause” here. My guess is it’s just a leading indicator signaling the dad is engaged in/places high priority on the family which extends to the marriage.
Aside from the cases where there is some kind of fundamental incompatibility being papered over by absence (which, sure, is a thing that happens, though), I fail to see how it could fail to be.
For example, if covid reduced number of cars on road and thus absolute number of accidents. Your saying you'd determine it's safer to drive because covid. However, in a relative sense, maybe pre-covid you had a 1% chance of being in an accident and during covid you had a 5% chance of being in an accident. What caused that? You can't just said covid made everything screwy and caused it all. You need to dig deeper. Are people running red lights because there are fewer cars on the road? Are people distracted because TikTok? Are they racing around trying to find toilet paper? Sure covid did all those things, but simply blaming covid is not really a useful analysis except in casual conversation; not academic research.
a father bonding with his children may also be more willing to avoid divorce.
but are these really significant factors? only research can answer that.
Couples where finances are stable enough that the person who didn't just pop out a kid can justify taking the time off are going to have the spare resources to maintain a marriage. They can afford all sorts of lifestyle crap that puts less stress on a relationship than living paycheck to paycheck in a double wide with a toddler running around causing problems. The correlation between stable finances and a stable marriage has been studied written about at length.