This is just a 1/2” nipple to extend into the tub.
A) this has been leaking for quite some time based on the way the inside looks- I would investigate before installing another nipple.
B) get the right sized nipple, but also you will need to seal around that hole- 1/2” pipe and 1” holes don’t math very well.
C) make sure the new nipple ( or previous reinstalled) is tight enough to not have leaks, I suggest maybe buying a bit of some better Teflon tape or a small amount of pipe dope to help with the process.
I think the argument that is often made is that we have discovered so little of our oceans that it’s possible we haven’t seen all the different aquatic species there are. Not suggesting Nessie is real, just the overall thought process I feel the believers use.