Alternative hypothesis: the reported number of drones isn't real (anything the Trump government says about "cartels" can be assumed to be made up). The military got increasingly on alert, with senior officers pushing to get a shootdown on one of the not real drones. Therefore the laser operators end up firing on the first drone they confirm seeing.
isn't this more comparable to the incident where a US Navy ship shot down an Iranian aircraft. They somehow convinced themselves it was a lone attack aircraft coming to intercept them:
Drones are not perfectly reasonable when semi-trucks filled with literal tons of drugs pass the border every day. They are used to smuggle drugs into prisons, but not really any better than the old hollow tennis ball trick and more trackable as well.
Compare the MH-17 incident. See also https://en.wikipedia.org/wiki/Gatwick_Airport_drone_incident , which also involved no confirmed actual drone.