He did assert that he could transmit a LOT of electrical energy wirelessly, and he convinced some well-heeled investors to finance him for some time while he developed that idea. But it never panned out -- not even close -- and I'm not aware of any trained physicist or electrical engineer who believes that Tesla's approach is possible today. High power wireless transmission of electrical energy requires close magnetic coupling or very high frequency (microwave) and directional antennas. Dangerous to anybody who gets in the way of the beam, and difficult to convert back to a more useable form - - say, to power an electric motor.
In his later days he was a weirdo and a con man. I don't know of any documentation that supports the notion that Tesla was "done in" by the establishment because he and his ideas posed a credible threat to their electrical monopoly and profits.
Sure did. But his now-known-to-be-outlandish claims regarding wireless transmission of high power electrical energy, and his shameless self-promotion and the cult following that grew from that detract from his genuine accomplishments in the field and industry.
He may have claimed that people could get (or ought to get) electrical energy "free" if transmitted wirelessly through the air. (If he did, then that was self-marketing bombast.) But as far as I know, he never implied that such energy would not have to first be generated by converting some other form of energy (e.g. oil or coal) into electrical energy. He was indeed a leading authority on the generation of electrical energy, so he undoubtedly knew that large amounts of electrical energy weren't just floating around in thin air waiting to be freely harvested.
What about his plan to "transmit messages, telephony and even facsimile images across the Atlantic to England and to ships at sea based on his theories of using the Earth to conduct the signals" = Wardenclyffe Tower on LI NY?
Marconi (and a few others, I think) beat Tesla to the punch on wireless (radio)telegraphy. Seeing that, Tesla announced that with his apparatus he would be able to transmit POWER -- which is a whole nother thing compared to transmitting radio waves that carry primarily information, and very little usable power. His promise to wirelessly transmit power was unkept.
Not sure what Tesla had in mind regarding using the earth to conduct the signals. Radio waves propagate through space just fine without an adjacent planet. That said, certain wavelengths of radio signals can travel farther on earth when atmospheric conditions are favorable -- the signal bounces back and forth (skips) between the earth's surface and the ionosphere as it travels over the horizon and partly around the world.
I got 1 and exactly 1 A+ in school -- in a class called Generation and Distribution of Electrical Power. (Should I mention that the main reason I got that superlative grade is that my dad, who was the Southern Division Industrial Power Engineer for the electric company, arranged a field trip for the class?)