Before going all conspiracy, most likely it's due to a poorly-implemented WiFi-enabled widget. There are devices that act as AP like the chromecast. This is th

Before going all conspiracy, most likely it's due to a poorly-implemented WiFi-enabled widget. There are devices that act as AP like the chromecast. This is then used by a smartphone app to connect and configure the device. I don't think the chromecast in particular is the culprit but I wouldn't be surprised a similar device was sending deauth packets due to an implementation mistake.