Not sure what you mean by 'took over'. There are multiple advantages of Delaware incorporation, primarily, taxes, of course. You don't have to set foot in Delaware to become incorporated there. I'm sure LeftowersLaw can enlighten us with more detail.
Most publicly traded companies incorporate under the laws of Delaware. Delaware has the most up-to-date law as a result of most shareholder actions are litigated there and because Delaware legislatures tries to attract companies for revenue.