Some do and some don’t. It probably depends on both the person and his age, as it does with everyone.
Rav Henoch Leibowitz, the Rosh Yeshiva of Chofetz Chaim, zatsal remarried. Rav Yaakov Kaminetzky, Zatsal remarried, but I don’t know how old he was when his first wife was nifter. Rav Elyashiv, Zatsal didn’t.
I wonder how many men this age get remarried in general. I would imagine that most don’t. And for a Gadol it’s probably harder than it is for most people because he needs someone on his level.