Funny, but my point is that if humans could’ve always had the power of telepathy, we wouldn’t need to invent languages and probably neither create most of the ideologies, tribalism, or belief systems necessary to gather a group of people together as one. If we didn’t have the capability to hide our true intentions, we might’ve evolved to follow the person / idea purely because they make most sense
I think OP picked ‘aliens’ because it would be an event where the whole world has to acknowledge that they exist and it would also contradict probably most of the current religions
“instant knowledge of everything”, except people’s true intentions, that’s my point