More likely you just put the guy in control of Ruthenia. There are specific conditions under which your claims are going to actually get you under control of the place you're pressing (you're de jure liege of the land which you're pressing the claim on or the person who has the claim is a member of your dynasty, mostly)
The province was independent for a moment before turning to Ruthenia. King of Ruthenia now changed.
Now I made primogeniture in my Empire but my kingdom of Hungaria is still Gravelkind and it doesn't seem too good.
UPD: And boy is it bad. I now have one province and everything else is divided between two kings. They are technically speaking my vassals, but considering I have slightly over 500 personal levy, it seems very very bad indeed. I even lost my capital somehow, and now reign in just build castle.