I would assume they put the centre of the coax to a clamp on the tower, then clamped the shield of the coax to the ground straps on the concrete base that are a part of the ground system. Then the used a tuner to bring it in.
We can all thank Audacy Las Vegas for shutting down 2 AM stations in Las Vegas and selling the property that these towers sat on to prop up their company's bottom line. So unfortunate that such a west coast powerhouse, 50,000 watt KDWN 720 should return to dust and no longer provide a public service to it's listeners. The original 3 tower directional array sat just off of Boulder Highway between Henderson and Las Vegas and was established in 1975. The demise of AM Radio is never a good thing, especially when we have nightime AM radio Stations powering down to about 27 watts and since they're on a co-located non directional tower, with a less than optimum antenna length and are expected to provide acceptable service. The industry sure has changed and not for the better.