Carnegie also created a vertical combination, an idea first implemented by Gustavus Swift. He bought railroad companies and iron mines. If he owned the rails and the mines, he could reduce his costs and produce cheaper steel. ... All these tactics made the Carnegie Steel Company a multi-million dollar corporation.
You can use the word "but" as a transitional word, but it is recommended to not use contractions. Likewise, your sentence will make more sense by changing doesn't to does not.
