My opinion:
well men are prone to being tempted. I think he wants something new or something adventurous. In your husbands field or status, a big "EGO" is a requirement. I'm not saying all, but it may prove as an advantage to motivate one's self in such a competitive industry. So its possible that this girl is providing here the necessary "EGO" boost.
So all in all most men like:
1. Something new.
2. Something exciting. (may spark burn-out motivation).
3. Somebody who has no boundaries.
4. Needs motivation.
5. needs inspiration.
6. somebody who can take care of him emotionally or physically.
7. Someone who listens and don't ask to much question
8. He is physically attracted to her.
9. Needs a way to express self or urge with somebody with no strings attached.
My point is, there are a lot of ways that men cheat, but its not because they just need to "cheat". Most of the time it has its reasons. Maybe emotionally your relationship lack that spark or because of his very stressful job sometimes a new and exciting "Activities" de-stress him.
Well just a warning, he may fall for somebody. If this partner buffers all his pains and listens to all his problems, it doesnt all come down to sex, its all because that someone seem to listen or accept him.
Men in nature is competitive. One draw back for competitive men is that you have to feed their ego and motivate them. Most of the time, the riskier the job, the more competitive the guy is, the more he seeks larger and exciting rewards.
Most men make this mistake. Temptation to the opposite sex is one of the most common mistake men do. Just talk to him about this, don't nag. He made a mistake and its up to him to correct this and you could go on with your lives.
Booow... Sorry ang haba. hikhikhikhikhik