No you are completely right the MC in triangle was wrong and did cheat, but he came clean and it did seem like it was going on to long(not making excuses, he was clearly wrong)but the wife had two weeks with the handmaid and when he gets back she doesn't say a thing, instead acts like nothing happened, as for the wife doing nothing, let me ask you this, if you would come come and see you wife/husband cuddling with someone in your bed what would be your reaction? She also kissed her on the shoulder if I remember correctly, to some people that is cheating.