You may be thinking of Marx's phrase about 'sharpening the contradictions' between capital and labor to hasten what Marx believed to be an inevitable conflict between them, but accelerationism is rooted in an idea of amoral Darwinian fitness whereas Marx's anxiety was that industrialists would capture the productive capacity of society and extract economic rents from it much as feudal lords had captured agricultural land and done likewise.
Although it's true that Marxists and accelerationists aren't the same group of people, they have made strange bedfellows recently, especially with the birth of xenofeminism. The disagreements in accelerationist circles stretch far beyond "amoral Darwinian fitness".
Marx was in some ways ahead of his time in recognizing that the productive capacity of society had already been captured (and had been so at least two hundred years before Capital was published), and the novel demystification of rent, profit and interest into surplus value. Despite the hints that Marx thought "things should get worse before they get better", there is stronger textual evidence for his belief in engaging in parliamentary politics. Whether that advice can ring true in today's 'democracies' remains to be seen.
No they don't; most Marxists (of whom I am not one) dislike the term and have little truck with accelerationist philosophy, such as it is - best summarized here: https://www.theguardian.com/world/2017/may/11/accelerationis...
You may be thinking of Marx's phrase about 'sharpening the contradictions' between capital and labor to hasten what Marx believed to be an inevitable conflict between them, but accelerationism is rooted in an idea of amoral Darwinian fitness whereas Marx's anxiety was that industrialists would capture the productive capacity of society and extract economic rents from it much as feudal lords had captured agricultural land and done likewise.