There are a few things that make this even more amusing than it already is:
1. Biden was "supposed" to be their one way ticket back into power.
2. The only reason their plan blew up in their faces was because, against all odds, Biden is still alive. By staying alive, he forced the Democrats to continue holding up the obvious lie that he was healthy, and it all came crashing down at that infamous debate.
3. His cancer diagnosis, as jarring as it was, only made things even worse for the Democrats. The fact that it was prostate cancer, which is known to be very slow to develop, made the big lie about his supposed "healthiness" even more obvious.
Looking back on it, it wasn't surprising how this all worked out poorly for the Democrats. But it's still impressive just HOW badly it backfired on them. There's almost no way it all could have gone any worse than it did.