Why would this be the case?
Will handing weights or streching cause it to detach?
Where exactly is it detaching from.
This whole thing is quite bizzare to me.
It's basically all just anatomy. Because the dartos is a very thin membrane inside the penis right next to the fat pad. Because of where the fat pad sits in relation to the dartos, basic movement like sitting and standing when you have a fat pad causes the fat to weigh down on and strain the dartos, eventually causing it to tear or break. The dartos is responsible for retraction of the penis (along with the cremaster muscles), especially during cold or nervousness.
No, stretching and/or hanging weights will not cause it to detach as those are completely different anatomical structures involved.
The dartos muscle is attached to the dartos fascia, so that's where it's detaching from. The dartos muscle runs through the penile shaft and around the testicles. Here's a diagram of penile anatomy where you can see the dartos muscle and the dartos fascia:
https://ars.els-cdn.com/content/image/1-s2.0-S0094014302000460-gr1.gif 
