'reason to explain' is a correct and usable phrase in written English.
You can use it to explain the motivation for something. For example, "I have a reason to explain why I can't attend the meeting."
There seems no medical reason to explain it either: our families have both been pretty robust.
On the flipside, there's no reason to explain why you left your last job in your cover letter.
The report's authors could find no reason to explain why in six cases houses has been attacked.
One reason to explain why England lose is football's inability to produce players across the class system.
Scientists may have found a biological reason to explain why two people who witness the same event will, years later, often have different memories of what happened.
I don't even have a proper reason to explain why I didn't like it, it just seemed so detached from itself.
Had it lacked a sufficient reason to explain its existence (and implicitly its contingency), the world for Leibniz would have existed of necessity.
"I didn't feel any reason to explain to them what happened or why I missed because I don't feel it's really anybody's business," he added, referring to the Giants.
But that hardly seemed like enough of a reason to explain why this month's most extravagant scandals are receiving little more than perfunctory attention in China, compared to the reaction among the other four-fifths of humanity.
I think what troubled some people was the ease with which Jeunet had crossed over from darkness to sweetness, without noticing a bump or seeing any reason to explain it.
Theologians have used his critique of reason to explain the leap of faith; architects have been inspired by his rejection of conventional rules to introduce a buffet of new styles, materials and shapes to building design.
