[kcg]

While I 100% think the controller in this situation made a terrible judgement call and likely shouldn't be working planes anymore, it's worth noting that that there are very specific regulations on multiple planes using the same runway (called Same Runway Separation). Specifically, for these types of aircraft (SRS Category III), the departing plane needs to be at least 6000ft down the runway and airborne by the time the arriving plane crosses the runway threshold. Heck, for smaller general aviation aircraft, you can have a plane land when another has landed and is still on the runway, as long as they are 3000ft past the threshold.

A different regulation (applicable only to radar environments, which AUS is) allows for a departure if an arriving aircraft is 2+ miles away from the runway, as long as there is at least 3 miles of separation within 1 min after takeoff.

All that being said -- it is possible to execute a squeeze play like this if everything is perfect, but you need the departure to go IMMEDIATELY. Trying this in low visibility was extremely reckless and incompetent.