Yes, the decay certainly goes back further than Trump. Before Trump there was Bush and before Bush there was Nixon. You could probably trace it back as far as the JFK and RFK assassinations, maybe further. Some see what is happening now as an extension of the Civil War.
But Trump is unique in that he:
1. Has never accepted his 2020 election defeat
2. Wields enough control over the rank and file of his party to have the power to terminate the career of any Republican who crosses him in any way, and has demonstrated the willingness to use that power without reservation
3. Demanded that election officials to commit election fraud (and was impeached for it, but not removed from office)
4. Incited a violent insurrection against the government and has suffered no negative consequences for it
It is his ability and willingness to use his power to promulgate the Big Lie that the 2020 election was stolen that makes him a much bigger threat to democracy than anything the U.S. has seen since the Civil War.
