"where did"his" wealth come from?" Geez, I don't know. "Capitalists" are not a monolithic group that all steal from workers or inherit wealth stolen workers. What difference does it make?
I guess you need a villain to support and explain Socialism/Marxism/Communism because without the evil Capitalist behaving heartlessly and robbing poor people the story doesn't work. What better way than to use the plight of poor working people, as in the sweat shops of 19th century England, to develop a faceless, nameless class of folks that prey on the poor. The class labeled "Capitalists" are obviously guilty as their money is witness to their crime.
The creators and leaders of totalitarian systems need to create villains to justify all or part of the coercive measures they employ to obtain and maintain control. Hitler had the Jews, Stalin had Cossacks, Mao had right roaders, and Pol Pot had people that wear eye glasses. Identification of enemies must be clear. Race, nationality, religion, ethnicity, having wealth, or owning a pair of eye glasses is easy and works. These enemies allow totalitarian leaders to mobilize the masses, whip up nationalism, race or ethnic hatred, and demonstrate brutally effective force to suppress the enemy. This demonstration, this killing of a few, or many, chickens keeps the masses in line.
Marx was a genius. But he had difficulty with money. Engels supported Marx financially for many years. Freddy was the son of a Capitalist employed by his father. So the support enjoyed by Marx was the fruit of capitalist exploitation. I guess this was okay as it was redistribution of wealth.
On the other hand, one could conclude the 'Communist Manifesto' is invalid and corrupt as it was a product of capitalism due to Engels participation. If you find all Capitalists guilty simply because they have wealth and means, then you might tar Engels with the brush of enemy of the poor. But his 1844 book was a clear indictment of the state of Capitalism in England at the time.
As a key element in Capitalism is freedom, the coercive element is minimal. Capitalism requires free, or nearly free, markets, free choice, free flow of information and a legal system which avoids political bias. A characteristic of Socialism/Marxism/Communism, from Marx to Lenin to Stalin to Mao to Jiang Zemin, is the expressed need to control information and public opinion. This control is essential to contain and mold public opinion in vilifying Capitalists and any other groups perceived as a threat to Socialism/Marxism/Communism.
Does it matter Engels took money from his Capitalist father and shared it with Marx?