"Marxism didn't happen BECAUSE of atheism." False. If it weren't for atheism, Marxism would not have existed.
Quote from Vladimir Lenin,
"Atheism is a natural and inseparable part of Marxism"
Xi Jinping, president of China, stated that members of the Communist party must be (exact words following) "unyielding Marxist atheists".
After reading Marx's writings, Ioseb Besarionis dze Jughashvili became an atheist.
Lenin, Stalin, Mao, Ho Chi Minh, Pol Pot, Castro, Marx himself, and Engels are all referred to as atheists in their Wikipedia articles. Lenin, Stalin, Marx, and Engels in particular are called Russian (for the former two) and German (for the latter two) atheism activists.
Quote from Got Questions Ministries (which explicitly condemns lying here https://www.gotquestions.org/Bible-lying-sin.html ) "In fact, communism is by definition an atheistic ideology."