Are the large existing predators on land, like lions, tigers, and bears, as well as sharks and killer whales in the sea, all species foreign to the Earth and introduced by extraterrestrials to worsen human existence?

This is quite true. All of the current species you mention and their variants were introduced by the interlopers. This is a broad subterfuge to make everything look natural and be consistent with the scientific precepts you live by, such as evolution through natural selection that, as well, are instilled disinformation to make you believe all of the difficulties you face, all of the dangers surrounding you, are a natural consequence of existence and simply something you must tolerate as best you can and survive if possible. As you know, and have asked, there are species of all kinds, all sizes, all varieties, among the animal and plant kingdom, and insects, and microbial realms that are foreign interlopers brought similarly, by the Extraterrestrial Alliance to darken the world and cause many kinds of suffering. While many of these kinds of organisms were present on the Earth in early times, following the first annihilation of humanity the world was cleansed for a reintroduction of humans, at which time all of the predatory species were removed to make the earth a loving nest for the divine humans to enjoy. Unfortunately, and as was foreseen, the honeymoon did not last.