Memes

Not trying to read too much into this if it's a joke, etc.

But

Marx was stating as an absolute statement of what he viewed as fact (and seems to be correct over a long enough timeline) that capitalism will fail due to contradictions

The Che quote is the less philosophical, more "in the shit" statement. Much like Lenin before him, these guys understood that the contradictions of capitalism lead inevitably, as Marx was getting at, to failures and collapses and it's at those moments that revolutionaries spring up and rile their base of support within the labor force of the country. Until that moment of crisis things were bad, but tolerable. During the crisis, conditions are intolerable and people are willing to do anything, including overthrowing the government/capitalist class and possibly dying for that cause. Because the alternative is death anyway. Or a living death.

On a side note, this is why there will never be (for any foreseeable future) a socialist revolution in the US. 1) material conditions are broadly "good" (although they are worsening) 2) there is effectively no leftist political movement in the US. There are a few thousand people who are genuinely anti-capitalist, anti-imperialist and want a revolution, but that might as well be zero in a country this size. Not anything new or crazy to point out that as people's conditions worsen further they will turn towards more and more radical leftist ideas or right wing ideas. Considering the racist undercurrents of the US and lack of any desire for any international cooperation amongst workers mixed with the (unfortunately extremely effective) FBI/CIA ops against US leftists in the past, there's only really one path that we're likely to head down...