It is simple, Arnold is what a republican should be like.
Arnold did not change, its is the GOP who lost its way.
On the environment:
On Democracy and freedom
So what happened to the GOP?
Citizens United happened which opened the floodgate to allow dark financing of politicians.
Before, American politicians acted based on ideology, after Citizens United, politicians started acting based on who gave them money.
Want to fix America, get rid of dark financing in politics.