It was likely a crocodile. There are no alligators in India.
From the article: "There are only two species of alligator that still exist today: the American alligator, Alligator mississippiensis, and the Chinese alligator, Alligator sinensis. Given these names, you probably wouldn’t be surprised to learn that these species can be found in either the United States (particularly in the southern states) or Eastern China."
From what I can tell, gharials mostly eat fish. The narrow jaw is likely adapted for catching fish underwater, says 'The gharial (Gavialis gangeticus): A review.' (1982) p535. While they have been observed to eat frogs, they did not eat a peacock nor rats, p536. "[V]ery large individuals are reported to eat other prey" besides fish [2].
"It is predominantly a fish eater, but occasionally takes turtle, birds and small mammals and is said to feed on corpses (Was it a someone’s observation or just a hearsay, if this declaration is based on some literature, please do cite it here)." [3]
I'm not saying they don't eat monkeys, only that catching monkeys on trees seems rare enough that it would likely be of scientific interest.
There's also only a few hundred adult gharials.
They share a habitat with mugger crocodiles. The latter have 'a broader prey base than the gharial including snakes, turtles, birds, mammals and dead animals' says the Gharial Wikipedia entry. However, it "has the broadest snout of any living member of
the genus Crocodylus"[2] so doesn't match faangguyindia's description.
Though the only other Crocodilia in India is the saltwater crocodile, which is 5x heavier, making muggers light-weight by comparison.
Finding information about gharials is complicated because there are "false gharials" in Malaysia, Borneo, Sumatra and Java, which definitely eat monkeys. https://en.wikipedia.org/wiki/False_gharial
From the article: "There are only two species of alligator that still exist today: the American alligator, Alligator mississippiensis, and the Chinese alligator, Alligator sinensis. Given these names, you probably wouldn’t be surprised to learn that these species can be found in either the United States (particularly in the southern states) or Eastern China."