Utter nonsense. Kings and the like could not exist until agricultural societies needed armies to protect them from invasion. Only from within such material circumstances and relations could divine right be wrought on a public imagination, whether it be monarchic kings or founders of PayPal.
And this is why materialism, Marxism or possibly otherwise, is worth defending.
This is exactly right, and Marx opposed revolutionary efforts in pre-industrial Russia (e.g. the Russian Revolution). He did advocate Russian support of revolution in Germany, but saw no use in revolution in pre-capitalist society.
Capitalism is a system in which those who control capital wield the most power, but without cheap enough labor to work the capital for a profit, capitalism will by definition give way to something else.
Realize capital has no market value without labor to work it. This goes for real estate too, which workers require to rest themselves just in time to return to work to turn a profit for those that control capital.