What causes the masses of men to obsess over and be controlled by this social materialism?

Although it is a Marxist concept, I think the answer to this is found in what is described as Cultural Hegemony by Gramsci. Those who control the State, whoever they are, place themselves in the position of power and make up the ruling-class. The ruling-class, being ruling, imposes its culture above all others, who see those at the top as a figure of success. The so-called "public opinion" can only exist if a centralized entity controls it, be it the State or the media, since not all people think the same, and they don't have similar worldviews, thoughts or ideas.

So for people's opinions to be similar, as they are today, people must be basing their beliefs on the same sources. These sources are the State, the media of all kinds, and even in many cases the Internet, because if we base our beliefs on the same pages as Wikipedia, we will probably reach the same conclusions, because we will only know one face of history. "Public opinion" can only exist as long as society is directed to the single thought.

I don't know if I gave myself to explain very well. But the fact that "economism" is so present in modern society clearly indicates to us that society is addressing a Marxism, which is essentially the mother of "economism", by describing human history as a struggle for productive and material factors. This process may be consciously, or unconsciously, it may be guided, or inertial, but the truth is that it is happening right now, and this is just one of the symptoms.