How is he (Trump) a threat to democracy?
Let's review:
Repeatedly/incessently stating that the election (and now all elections where he or his pick loses) are 'rigged'.
Stealing documents belonging to The Presidency (no longer him)
Fund raising based on lies fully knowing he's fleecing his own followers, then mis-appropriating those funds for personal gain/use
Calling The Press the 'enemy of the people'
Exploiting an already divided nation for his own power
There's not enough band-width to list everything, but suffice it to say he's definitely a threat.
Now before all the false-equivalent responses start pouring-in, I agree that Biden's cognitive abilities escape him (and I am in NO WAY a supporter of many of his policies). For some reason many supporters of the former president believe that since the majority of the voters chose Biden (and HRC for that matter), then we're all beholden to his every whim and decision (believing our 'dear leader' can do no wrong) because that's the way they feel. And let's not ignore the fact that DJT instilled that 'feeling' in those that felt forgotten/passed-over/whatever to the degree that he can 'shoot someone on 5th Avenue' and not lose a single supporter.
Let that fact sink-in...
Gotta admire the lengths to which Trump followers will go to defend the indefensible (Cohen/jail, Bannon/sentencing, Weisselberg,sentencing, Flynn/pardoned, Stone/pardoned, Proud Boys/convicted, Oath Keepers/convicted...again, not enough space.
So unless Hunter Biden and his laptop were used to pay-off pornstars, concoct tax evasion schemes, conspire w/foreign adversaries, devise a Wikileaks dump or attack Capitol Police, there really isn't any comparison.
I do know for a fact that all of his followers hate (and I mean really hate) the liberals, enough to violently storm The Capitol...can you imagine if it were a BLM protest? There wouldn't be one protestor alive. They'd still be trying to clean the blood off the portico