I actually hope that you’re right, because that would mean that the cabal that intends to overthrow democracy in the US is much more stupid than I had thought.
In the first place, the whole idea that a candidate might be prohibited from dropping out and/or that the party would in that event be prohibited from choosing a replacement is farcical on its face. Beyond that, the SC explicitly ruled after the 2016 race that the DNC is essentially entirely free to do whatever the fuck they want. Additionally, they recently ruled regarding Trump’s removal from ballots that states are not free to do whatever the fuck they want.
What that means is that in order to rule in such a way as to deny a replacement would reveal the complete and utter corruption of the system almost four months before the election, which would be an exceedingly stupid thing to do.
The far better strategy would be to just bide their time, let the democrats do whatever they choose to do, then implement the coup after the election (and preferably as close to the inauguration as possible) so they can accomplish it all at once, then hide behind the president’s newly granted dictatorial powers.