This almost makes me suspect that the Facebook executives behind this decision are secretly die hard pro-Trumpers.
Sure, it's definitely a bit spooky that people are going around saying the election was stolen when, as far as I can tell, there's no hard evidence of widespread cheating. (I'm open to changing my mind given sufficient evidence, I'm just saying that I haven't seen it yet.)
But this is the equivalent of Facebook saying "hmm, looks like there's a fire going on over there, better go and dump a barrel of oil on it to put it out". Of course people are going to notice that their posts are being deleted. And even if they didn't notice, Facebook is loudly and publicly announcing that they are removing those posts. This will naturally result in those people saying, "aha, this confirms that there is a liberal elite conspiracy against folks like me". It will only make them more certain that the election was stolen.
Honestly, I can't say I blame them for suspecting a conspiracy, given we've had similar moves by other tech companies. As a generally left wing person, what am I supposed to say? "Yeah, we know that all these social networks are acting all biased and stuff against people with your opinions, but it's not actually a conspiracy, just a bunch of people without the ability to predict what others will make of their actions all being idiots at the same time due to simple memetic contagion." I think that's actually what's going on, but I can definitely see how from the other side it looks like a conspiracy.