Bullied wood pigeon

I have 2 or 3 wood pigeons that regularly visit my garden. A couple of weeks ago i thought one had fallen ill. It was sat in one spot for a good couple of hours. I monitored it and eventually it got up and i saw it had a limp. It remained in the garden hardly moving most of the day and then flew away in the evening. Over time its limp got better. Then a few days ago i saw two large magpies attack the same wood pigeon (i recognise it from its displaced feathers) and they knocked it out of a tree. They were brutally pecking it but i scared them off. After the attack the pigeon stayed in place for nearly 5 hours before it flew away. And then this afternoon i found the same pigeon again near the back door. It has tucked itself into some bedding plants and appears to be hiding, and has now just been sat there for around 4 hours not moving - and i’m guessing it has been attacked again. I put a small try of food nearby and am considering trying to help it if it doesn’t eventually fly away. I’m interested in why the same pigeon keeps returning, and why the magpies keep targeting it. We have other wood pigeons but they don’t get attacked (although the magpies are hyper-aggressive and regularly swoop and chase off other birds). The whole situation is bizarre and very sad - the pigeon looks depressed and bullied, but otherwise seems alert and disease-free, but seems to keep returning for more punishment. Does anyone know why it might just sit there for hours afterwards - could it be a stress reaction, or maybe it’s in pain after the attacks?