There were cars before the Model T, but only for the rich. Ford made cars affordable for everyman. That changed everything.

There were books before Gutenberg, but only for the rich. His printing press made them cheap enough to print newspapers. That changed everything.

Before Bessemer, making steel was extremely expensive and rarely one. With the Bessemer Process, vast quantities of steel could be cheaply made. That changed everything. Google says:

"The process revolutionized the industry by reducing costs and increasing production, making steel accessible for major infrastructure projects in the 19th and early 20th centuries."