Tubes work by real, actual "magic".
The tubes direct and modulate streams of electrons. Except electrons really aren't anything. As far as physicists can tell, and they've been studying electrons for 120 years or so, electrons HAVE NO EXTENT. Not just very small. Not even microscopic. NO attempt at measurement has found an actual discernible size to the electron. And due to quantum rules, you can't really say they are here or there, you can at best come up with a rough probability of where one may be. Even worse, the detailed electron equations only work for a single electron circling, or anyway, near a single proton.
So tubes use things that have no size. In my book, that means they really don't exist. Except they do eventually hit a plate and make a click. So something goes on between cathode and plate but not anything you can see or even fully theorize or explain.
And, ummm, if that isn't weird enough, while they have no size, they have something akin to "spin". Worse yet, they only have 1/2 a unit of spin. You effectively have to spin an electron 720 degrees to get it back to its original state. Not speculation, 1/2 spin is the only amount that fits into dozens of electron equations. See:
Even worse, you can get a rainbow or interference pattern from an electron stream, so in some sense they are not particles but waves. Again, waves that come in discrete but invisible bundles. Weird enough?
Sure, you have your Spangelburg books with equations that help model tube behavior at a high level, but deep down things get really crazy.
So we are fully justified in calling it pure magic and enjoying our hot little friends, the tubes.