It means people invent invectives to satisfy their own deluded psychologies, independent of any merits of what they say. They fabricate narratives that make it easier for them to live with themselves, and disown responsibility, in favour of incorrectly trying to blame someone else.

Frequently the target of their blame is someone ( or something ) successful, since this has the most pay off for them. It has the most pay off for them because the large difference in success between themselves and their target gives them the most serious dissatisfaction, which they seek to correct, not by taking actions which may improve their situation, but by believing delusions which may diminish the difference that so vexes them.

So the hater tries to pretend that the successful is "wrong", and this makes them feel doubly right, in that they are "better" than the one who is objectively better than they ( by being "right" and the other "wrong" ), and, further than that, that even the objective measure of success is itself somehow flawed, because they purport it to be founded on a great injustice which they fabricate for the very purpose of making themselves feel that much less inadequate in comparison.

It's a highly compelling, and widespread addictive delusion, because it's like a drug. People get the feeling of success and achievement without actually doing anything to achieve that. They get the neurotransmitter dump, simply by fabricating for themselves a delusion ( their hate filled invective ) in which the successful is not, and they are right.

The tricky part is separating all this from what is actually true. Separating the narrative, from the what is.