We have generally seen that the Indian stock market reflects the trends in the US stock market. Therefore the question arises "Is the Indian market heavily dependent on the US stock market?" Or in other terms, are the Indian stock market dependent on the FIIs (FIIs are nothing but the Foreign Institutional investors who invest money in the global markets)?
India is observing fast economic growth for the last few years and as a result, the inflow from foreign investors across the world into the Indian stock market has increased. Because of this foreign investors' activities in the market have a large impact on the Indian stock market.
Ok, so far it makes sense that market volatility is controlled by FIIs. But why Indian market reflects the global markets?
The FIIs who are investing in the Indian stock market are making decisions based on the global trends or maybe their own local market trends. So because of the decisions that FIIs take and they are the major chunk of investors in the Indian stock market; the Indian stock market reflects the trends of the global stock markets.
Let's go further and answer the original question of "Why Indian Market are dependent too heavily on the USA stock market?"
The USA is the largest economy in the world and most countries' economy depends on exporting goods and services to the USA. Also, since the USA is the largest economy therefore a lot of economists analyze the USA stock market. The above two mentioned are primary reasons why any negative or positive news in the USA stock market impacts the Indian stock market.