The Chrome Web Store—where you get Chrome browser extensions—is controlled by YouTube's owner Alphabet/Google. Even an extension ostensibly for this purpose—like the obviously named Video Downloader professional above—states right up front in its description, "The download of YouTube videos to hard drive is locked because of restrictions of the Chrome Store." In general with Chrome extensions, the download of any RTMP protocol video (protected videos) or streaming video isn't possible.
Do you prefer to avoid installing software? Video download helper sites do the download work for you, providing conversion and then a download link—you don't have to install anything on your PC. It can take a lot longer, depending on the size and quality of the video you want—a typical two-minute movie trailer in 1080p can be around 30MB—but you can't beat the convenience.
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