US Capitol riot: How can an Army reservist, known to be an extremist, receive a secret-level security clearance?

(CNN)An Army reservist who federal investigators say has secret-level security clearance and a long record of posting his extremist views online was among the latest wave of rioters charged by federal prosecutors in connection with the January 6 Capitol insurrection.

Source: US Capitol riot: Army reservist with security-level clearance among the latest charged – CNNPolitics