You seem to be assuming that Raffles didn't care for Singapore, how can you verify that assumption?

What would happen if Raffles didn't leave Singapore and stayed in the country with Farquhar ?

Why are you saying that? Does that mean that just because Farquhar made the initiative to communicate with the locals, he is considered the founder of Singapore?

Can you give me an example of Farquhar trying to earn the trust of the people and trying to find out what problems the people were facing?

Even though it was Farquhar who was responsible for most of Singapore's development, it was Raffles who wanted to make Singapore a trading port, so if Raffles hadn't set eyes on Singapore at that time, Farquhar wouldn't have been able to accomplish this.

Raffles found that Farquhar had done a bad job of raising the city of Singapore, he also introduced opium selling into Singapore in order to raise more money to build Singapore.

Raffles founded Singapore and Farquhar was just a subordinate for Raffles. So it was normal that Raffles gave he duty of turning Singapore into a successful city and left the city to Farquhar to handle.

Raffles was responsible for Singapore's boost of economy

He increased the economy of Singapore by using the Straits of Malacca as a trading route.

He established free trade and thus many people came to Singapore to trade with each other, boosting Singapore's economy.

Raffles was responsible for Singapore's boost of economy