"Beamforming" (and the author is right to be skeptical of that term) is some really cool magic. My understanding of the history is that a lot of the technology comes from military radars. Development there was driven by power and compactness, and the relatively novel need (at the time) of building a radar that could both track targets and scan for new targets at the same time. Before that, you'd have a scan radar (antenna turning round and round), and a tracking radar (antenna pointed at the target). With beam forming tricks you can scan without moving the antenna, and then quickly jump back to get some additional tracking data. These days track-while-scan is easier because we can use computer models to do things like track interpolation, but back when this stuff was being developed that was much, much harder.

Twenty years ago when I was doing my PhD work, we were working primarily on passive radars (technically something called Passive Coherent Location (PCL)). With passive radars you have some transmitter of opportunity (a TV tower, or cell tower, or somebody else's radar), and want to observe the energy from that transmitter bounce off other things. One thing that's hard about that is that the transmitter is usually closer than the target, and the target doesn't reflect all its energy, so the returns from the target are many order of magnitude weaker than the direct return from the transmitter. So you need to design your antenna or antenna array very carefully to get only a small amount of the transmitter power (don't want to saturate your analog side), while getting as much of the target power as possible. You can do that with static antennas with "manual beamforming", but dynamic approaches allow you to correct for things like multi-path and changing atmospheric conditions.

Our particular work was in very low cost versions of this, with the end goal of spreading transmitters all around ("netted radar"). Good for cost, good for sensitivity, good for counter-stealth, but meant a very limited budget for any station. With the technology available now for building antenna arrays, we could have done so much better than we did back then. Amazing how the technology has changed in just a couple decades.

This seems to have been driven by consumer products. Wifi, cell phones, bluetooth, etc. The miniaturization, cost reduction, power reduction, etc. The technology came originally from big military radars, but what's driven the revolution seems to be the volumes and demands of consumer products. That's definitely going back into military and high-end civil technology, which is going to drive even more interesting requirements. A fun case study in technology.

(I have no non-public information on military radar technology, US or otherwise.)