When Tom's wife finds out he was passed over for promotion, she says "Screw it, they don't deserve you. Quit! I will go back to work full time."
two days later when she learns about the harrassment she says "Apologize, go back to your job and get along!"
If she was supportive of him quitting before, why would she not be now?
Because people change jobs all the time, often because they want to move up the management ladder and can't do it at their present company.
On the other hand, having been accused of sexual harrassment could ruin his career and his reputation. If he were to quit at that point, anyone who checked his references would see that he had essentially resigned his previous job in disgrace. Though he doesn't know it yet, things would look even worse as Johnson and Garvin were planning to pin the production problems on him as well. Begging for his job back and apologizing might make Johnson rescind her accusation, so he can at least have steady work.