The primary concern of which artistic style was direct observation of society and nature, as well as political and social satire?

That would be Realism.

Realism is an era in art and literature which originated in the 19th century. Some of its characteristics include portraying real life as it is, observing nature and the world around us and depicting it faithfully, criticizing politics and the society in general (which is why satire was quite common during this era).