HINDALCO, an aluminum factory located at Renukut, was primarily set up there due to option 2 - abundant supply of power. Aluminum production is highly energy-intensive, therefore, an abundant power supply is crucial. Now, let`s discuss the other options for clarity.

Option 1 - Proximity of raw materials: Although important for a manufacturing factory, the production of aluminum mainly deals with bauxite which is usually transported from mines and not specifically near Renukut.

Option 3 - Efficient transport network: This factor is crucial for transporting the finished products, however, it isn`t the prime reason for the factory`s location.

Option 4 - Proximity to the market: The market location isn`t as critical for heavy industry like aluminum as it can be transported to diverse markets.

So the key reason HINDALCO was set up at Renukut is due to the abundant power supply available, essential for the energy-intensive aluminum production process.