I don't understand why the bluetooth-stealing happens so often. I'll literally be in the middle of a podcast on my phone, and my iPad in the next room (on which my kids have been watching something) will take over my headphones. There's no change in state on either device (not stopping/starting), and I haven't moved close to the iPad (and the iPhone is much closer, in my pocket). I just have to turn off bluetooth entirely on the iPad to avoid this.
I use a USB/bluetooth headphone DAC/amp. Most of the time, I plug it into my work laptop and listen to videos/music while I work. Sometimes, if a video ends or if I pause playback, my iPhone (which INSISTS on connecting to the amp) will take over and start playing music.
I really wish you could turn off auto-connect to bluetooth devices.
Bluetooth is basically the devil though. My Bose speaker cant handle the fact that I always want my Android phone, and keeps insisting that I really want my child's IPad.
