Why did India, which controls Nepal, stumble in Sri Lanka?

Since ancient times, small neighboring countries have been annexed by neighboring powers. From the map, India is also close to Sri Lanka, but Sri Lanka has never been annexed by India. This does not mean that India does not want to be annexed, but that it cannot be annexed. The main reasons are as follows.

First, although the Indian mainland is very large, it used to be divided, and it was not a country at all, let alone powerful. Moreover, it is divided into dozens of local States, which are constantly at war with each other and invaded by foreigners, and their own problems are very headache. How can you manage Ceylon if you can't beat yourself? So ancient India may want to occupy this place, but it is because it has no ability. For thousands of years, its own affairs are uneven and there is no expansion ability. If the British hadn't come and forcibly unified all the areas around India, I'm afraid India would still be divided into dozens.

Second, after the British came, they forcibly unified India and brought Ceylon into their sphere of influence. They could have been directly assigned to India, but the British kept Ceylon independent. Because the British saw Ceylon Island in the real center of the Indian Ocean, controlling it basically blocked the throat of Indian Ocean trade. So it can't be given to India. This is an arrangement made by India to stabilize its rule and safeguard its own strength and global trade. Therefore, I have no ability, and my English father won't help me. Of course, I can't occupy it.

Third, when Britain withdrew from India after World War II. To contain India's strength and future risks. There is a divided India, when the two sides broke up, and no one obeyed, that's all. Since independence, it has never stopped, especially after the 1962 war, India did not dare to act rashly. From a realistic point of view, India does not have the ability to fight at the same time. It is even more impossible to win Ceylon. In fact, the heart wants something, but it is powerless. In addition, the Soviet Union, India's biggest backer in modern times, did not dare to do anything internationally after the fall of 199 1, so it never dared to do so.