A couple of generalized insights from someone who has worked for a federal land agency.
-The Bureau of Land Management is an agency that manages land owned by the United States' Federal government. It permits leases,, and regulates activities such as mining, drilling, and grazing on some federal public lands. It has a different mission than the National Park Service, the US Forest Service, and the US Fish and Wildlife Service.
-Across all agencies, Federal land management in the US is a mess and has been for over a century. The US government has not enforced regulations consistently, and in some cases not at all. This is not always the fault of the government, since the regulations are often poorly worded and open to legal interpretation. Different administrations enact different policies, making consistent management impossible. Furthermore, these agencies lack the manpower and efficiency to consistently enforce regulations in some of the most remote locations in the country. As a result, multiple generations of some families have been allowed to engage in activities that were not legally permitted, or used the land without following regulation. For example, some ranchers have been tacitly allowed to graze in areas without permission for decades. Complicating the issue is the fact that some people, by being present on certain lands before it was owned by the government, had some rights grandfathered to them. These rights are not always transferable to descendants, which is something descendants tend to get upset about.
-In recent decades, the Federal government has started to increase both the number of regulations and the enforcement of those regulations on federal lands. This has, understandably, upset people whose families have been using the same land in the same way for decades. Under recent administrations, particularly the Obama administration, use of (and in some cases access to) federal lands has been much more controlled.
Now this may not sound like a big deal, but look up a map of federal lands owned up the United States and you'll find that in some Western states, such as Utah, the US government actually owns over half the land. There is a huge amount of tension between residents, state governments, and the federal agencies over how to use these lands. We're talking about millions of acres of land and billions of dollars in potential mineral and grazing rights in states without much economic development.
In addition, you have the added headache of family identity. Many of these people have grown up as ranchers and miners, and feel like their way of life and their heritage is being stolen from them. They aren't exactly right, since some of them have been criminally using the land, but they aren't exactly wrong either since they have been allowed to use the land for multiple generations.
It's a big mess we've inherited from past generations, and a mess on which both sides are kind of right both sides are kind of wrong. As the agencies have tried to clean the messes up, it's led to a lot of tough decisions and hard feelings. I've seen first-hand how emotional the arguments get, and it always because all parties involved truly do love the land in dispute. It's extremely hard for people not directly involved in the legal battles to understand, but the fight is more than about being able to graze cattle or drive a truck on a beach. It's about big, fundamental issues like freedom and family.
What I recommend is to not stereotype the sides in these types of cases. Often, the "kooks" opposing the government are kooks, but they also just as often have legitimate grievances about how the federal government has treated them. At the same time, the government is often right in the larger sense that the people shouldn't be doing whatever they've been doing. And often the people who get yelled at for the government policies aren't responsible for the policies, they're almost always seasonal employees who love the outdoors and don't have a say in the matter.
That being said, while I don't know enough about this case to be sure what happened I am not defending taking over a building at gunpoint, so please don't take what I've said as being for or against anyone in this case.