As they say, ex-communists make the best capitalists.
Also, to be clear, it's a common understanding in Marxism that capitalism is a stage of socialism. The "capitalism and socialism are opposites" rhetoric is too simplistic.
Socialism is different but built upon capitalism, in a similar way, for example, to how electric cars are different but built upon gas cars. Marxism opposes neoliberalism and other forms of governance that leave capitalism unchecked, but doesn't reject everything about capitalism— "just the motor, gas tank, and other harmful parts" you could say.
[1] https://www.reddit.com/r/CapitalismVSocialism/comments/vlxxv...
[2] https://www.reddit.com/r/CapitalismVSocialism/comments/1g5kd...