What is the reason why the trend of the media gravitate towards more and more shallow values and mental?

The movies are following the lead of American society in general, just providing what the public seems to want and can relate to.

They are trying to sell what people will buy. The media is a business, just like any other business.

In the last days of Christ, the wrong becomes right. So reality tv shows reward people for lies, and cheating and stabbing others in the back. The bigger moron you act like, the more prize money you win. I think the new social trend in tv, movies, media in general is to behave badly and then get rewarded for it.

Just follow the money! But I think you might be suffering from nostalgia. You can dig through the junk being produced today and find some real gems, these are the films, books, flash animations, etc. that will be the classics in ten years. If you actually look at a representative sample of media from any era you'll find that the schlock far outweighs whatever has persevered and become classic.

The last sentence answered your question I think...

The media has a "populist" mentality of giving the people what they want. This way the media could sell advertising and stay in business.

Psychology, feminism and liberalism. We have strayed from the concept of self control in our battle against God, and begun to replace it with natural human emotions or instincts. You must first understand where it all began. Look up Margerett Sanger, the founder of the Feminist movement. Then research eugenics, which was the science Hitler used in an attempt to create a supreme race. All of this is being done subtly in our society to weed out the poor, and the disabled. They have been working for a very long time to rearrange societies mentality on right and wrong, and played on the emotions of the majority to confuse them. This is how abortion became legal, and it is now why sexual deviant behavior has become a trend. We have been programmed to sympathize with the deviant rather than the victim. It was no accident that the pedophile has been turned into the victim and the victim has been tossed aside. The victim is weak, and often portrayed as mentally unstable by the media. The goal is to make only the strongest survive. The population eats it up because it means no more consequences for deviant behavior and no more rules to the natural order of things. We can react on our first instinct and be considered healthy, but if we use self restraint we are psychologically ill and considered bias towards everyone else. ;-)