So first understand that the land belongs to the US Government. People were grazing on federal lands without the government’s permission before the creation of the Taylor Grazing act (1934). At that time, Congress decided to start charging a fee for grazing on their land. In that law, they created the Department of Interior Grazing Office for the charging of fees to graze on US Government lands. This office was later rolled into the BLM.
It is government land, the Congress has exclusive legislative authority over that land per Article 1 section 8 of the constitution, and they decided to start charging fees and for a while, Bundy was paying those fees.
Article 1, Section 8 very specifically lays out what land the federal government can legally own.
10 square miles for seat of federal government (Wash DC), and plots or sites necessary for forts, arsenals, dry-docks and needful BUILDINGS.
There is not one thing in The Constitution which gives the fed gov legal authority to own large tracts of land just to own them.
Also, the deal between Nevada and the fed gov at the time of statehood is completely non op and non legit by any reasonable reading of Art 1, Sec 8.
Lets not forget that corrupt politics and bad judgements from courts isn’t a recent invention.