Russians aren’t conscripted for life. So I’ll give them the benefit of the doubt on their character and conduct. Besides, those types are usually quite adverse to military service so would likely avoid it after getting out.
They were private Russian contractors advancing on a US base securing nearby oil facilities. It was likely done with a wink and nod from Gazprom, directed from Russia.
They knew they were advancing on a US base and were warned repeatedly. They died due to greed and callous miscalculation.
Who do you think are military contractors? Most of them former military and they are out of military and into contractors because it pays more and there are also different standard on discipline. Also military would never take a man with a criminal record which is not an issue for a private contractor.