Monarchism is the favor of establishing and preserving a monarchy as the form of government. A monarchist, however, is someone that supports this form of government by principle and not necessarily of a person, which would be the Monarch.
Some Canadians are monarchist, some Brits, Aussies, Kiwi's are monarchist, too. Some are not. They all live in a monarch, underneath the Queen of England.
I could ask the same thing of a communist why he would be a communist in a country that isn't communist.
I read Leviathan and Hobbes is definitely an absolutist. I don't particularly agree with what Hobbes put forth (not that it is wrong, but it wouldn't fit our tradition) about absolutism and I have a hard time with his more liberal thoughts (I do agree with some of his stuff, just going over what I think of the work I have read).
Another point of contention with Hobbes, is he's a radical and a skeptic. Both of which I am neither, the latter more than the former.