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.
At the time, the US government was involved in a major war to help make Europe safe for communism. They seized Tesla's stuff in case he had any info that the anticommunists could use in their war effort. That said, I don't doubt that the government agents would lie about what they did or didn't find. And their report was classified for a long time.
But I think it's safe to assume that if gov had found the plans for the particle beam death ray weapon that Tesla allegedly claimed he had invented, that gov would have developed and used it.