Ever since Robert Redford starred in The Natural in 1984 I think due to the popularity of The Natural it began a new trend in sports movies with baseball themed movies. Soon we had baseball based movies such as Bull Durham in 1988 and Major League in 1989 with Major League II later on and I think people thought baseball themed movies would do well in theaters. Then we had Kevin Costner's Field Of Dreams in 1989 and you can see why baseball movies are huge in sports movies. But once The Natural came out in theaters in 1984 The Natural is to blame for the popularity of baseball themed movies in the 80's

I also think why baseball themed movies became popular in the 80's was because Major League Baseball was a hot sport during the 80's and to catch on the sport's popularity movies featuring baseball were just starting to be big. I bet you watched Bull Durham or laughed at Major League when they debuted in 1988 and 1989. But I think as I mentioned The Natural is responsible for baseball themed movies to become popular in the 80's