the husband knew he's wife was an obviously extremely private person for God knows what reason, he should have then respected her wishes. 

Personally I find it strange and messed up to end a marriage for such a reason but then the wife in question might think the same about the reasons why I'd ever consider leaving my husband! 

And we don't know the nature of the ill fated kiss...was it just a smooch or waay more than that. 

All the same,supposing this to be the only reason, then I hope they are counselled  and reunited..shame to break up a home over such issues that Inshallah can be worked out!