Why did India stumble in Sri Lanka to control Nepal and split Pakistan?

I stumbled in Sri Lanka mainly because India chose the wrong direction. In South Asia, India is a military power. India launched three wars between India and Pakistan. In addition, India annexed Sikkim, controlled Bhutan, contained Nepal and split a Bangladesh. From these behaviors, we can see that India is not a peaceful country. But in Sri Lanka, India failed. Why is this?

One is geographical location. The geographical position of Sri Lanka is different from that of South Asian countries, because Sri Lanka is a natural island country, facing the South Asian continent across the sea, and the ocean is a natural barrier, which prevents the effective invasion of Sri Lanka by Indian forces. This geographical advantage makes Sri Lankans not worry about Indian invasion.

But it was not easy for India to invade Sri Lanka before, but it supported some organizations in Sri Lanka. In the 1970s, the Tamil Tigers were formally established. After its establishment, this organization developed rapidly and gradually became the most powerful anti-government armed group in Sri Lanka. India is the driving force behind this.

While the Tamil Tigers supported by India are developing rapidly, the Sri Lankan government forces are getting weaker and weaker. After seeing this situation, Sri Lanka chose to take the initiative and actively attract some international forces to provide support. In this way, the LTTE and the Sri Lankan government are deadlocked. At this time, India saw that it could not attack for a long time. Later, the Indian government gradually realized its mistake. If Tamils are really in charge of the Sri Lankan regime, it is difficult to guarantee that Tamils in India will not follow suit.

1987, Indian prime minister rajiv gandhi decided to change his strategy from supporting rebel groups to supporting government forces. Fortunately, he immediately turned against LTTE and signed the India-Sri Lanka Peace Agreement with the Sri Lankan government. From this process, we can see that India's efforts in Sri Lanka have finally achieved nothing in Huasong.