With such a large estate, Probate would be required in Minnesota regardless of whether or not there is a will. If his compound or other real estate was owned in "Joint Tenancy" it could pass directly to the other named owner/owners or "Joint Tenants" on the deed thus bypassing probate. The same would be true of jointly held accounts, payable on death accounts, or life insurance that names a beneficiary. If he had a total of $50,000 or less in personal property, then probate can be avoided. Obviously, that is not the case.
The term "probate" actually comes from the Latin "to prove", and refers to the legal process of proving that someone had a valid will. They had to "prove" their claim to the estate. My guess is that this will be a very complex probate process that could drag on for years.