No one ever explains what is currently preventing them from declaring martial law now. The idea he needs an excuse implies you think that, if he did it now, the regime would collapse and he'd be tossed out. Which is utter fantasy. NOTHING prevents him from doing it now and he'd be immune.
The regime needs MAGites to believe for as long as possible they're only going after the woke so they'll remain devotees while democracy is gutted via perverting the current system until, b4 they know what hit, the police state & martial law are slipped into place against everyone & the job is done.