In order to understand art we always have to analyze in what period the artist lived or lives, what was happening historically in the world at those times, only then will we try to understand what was going through the artist's mind when he made that work. In this case, we go to the year 1871, which was the year when Posada had his first important job. He came to make eleven lithographs for "El Jicote," let's keep in mind that at this time most Mexicans could not read or write. So it was crucial that the illustrations in the newspapers were very attractive so that people would buy them. Posada, as you can imagine, was very good at that, so good that today we are talking about him. And the whole world is still intrigued by the figure of La Catrina.
Posada specifically addressed the middle class, in his drawings and lithographs we can see that he exhibited the inequalities and the suffering of the people in a very intelligent way through satire. The skulls he drew showed the excesses of the upper class. Let us remember that Posada lived during the Porfiriato and witnessed the increase in inequality between classes. Let's take the example of the catrina that Posada originally called her "Calavera Garbancera" if we see the hat she is wearing has feathers like those used in Europe at the beginning of the 20th century, the term garbancera was for those of indigenous blood who pretended to be Europeans. The skull does not have clothes to highlight the hypocrisy that these people lived as if to imply it does not matter how they dress or how much money you have at the end in the face of death we are all equal. Or as Posada once said: "Death is democratic, since at the end of the day blond, brunette, rich or poor all people end up being skulls."
Many artists, including Diego Riviera, were inspired by Posada's skulls, especially the Calavera Garbancera. At such a level that Diego in one of his most famous murals "Dream of a Sunday afternoon in the Alameda Central" paints the garbancera skull but this time Riviera paints her dressed and nicknames her Catrina. After this mural, La Catrina achieves unsurpassed fame.
Posada in life like many artists was not as famous, as he is after his death.
Sources