I had a relative, a man, who remarried fairly quickly after the death of his wife, like 1-2 years or something. I think he just needed a woman, he needed someone to cook, run the house, etc. He was a high-level executive. I'm sure he didn't want to be alone.
His wife had been dying for a long time so he knew it was coming and had time to prepare. I think for spouses of people who die suddenly it might take them longer. Everyone is different though.
This is similar to my dad. He started dating soon after my mom died and was married within two years. He is a man who just really appreciates the companionship of a wife, and while in some ways it was hard to see him move on so quickly, in others it was a testament to how much he valued marriage and the sort of partnership he had had with my mom. My siblings and I were all supportive.
He had nursed my mother through four bad years of illness, which I think did make him more ready to move on.