I think Oath Keepers is still alive and well.
I know several service members and LEOs of two different departments (not in Metro DC) who are dues paying members of Oath Keepers.
Yet, the SPLC labels OK's founder (and therefore the entire group) as "extremist". They associate them with the sovereign citizen movement as well as white supremacist movement.
Of course they do, the government must fear them. Better to smear their names than allow the citizenry to know these people exist in government. So they use the SPLC mouthpiece to disparage them.