A person can begin dating immediately (assuming there is not a shloshim involved, as in acase of spousal death). There is no wait period for a man to get married after giving a Get (except as noted, if marrying a widow or divorcee of less than three months). There is a three month wait for the woman (unless she was never married and is marrying a divorced man, in which case she may marry him right after his divorce).
Emotionally, and with sensitivity to the possible children from the previous marriage, a man and woman may wait several months to either begin dating or to get married. But it is not halachically mandated that they do so, except as noted.
In the case of a man who has lost his wife, no one should be in his shoes and judge him for wanting to remarry quickly. Studies have shown that when someone had a happy marriage, they want to feel that happiness again, quickly. Some people mourn for a long time. Others are able to get back into life more quickly, even as they mourn. No one should judge. Same thing applies to a divorce. Some men cannot live without a wife and will start dating immediately. Some have been burned and don’t want to know about dating. it is not up to us to decided when it’s right for them. Hashem already gave us the proper guidelines.
The only reason Cedarhurst thought 9 months, is that he was confusing the IDEA of a woman having to wait three months to see if she is pregnant by the first man (something she would know most likely within the first trimester), with the actual pregnancy period of 9 months.