I don't think it has anything to do with bulls, but with glass.
Before glass was formed in sheets, the liquid glass was 'blown' into a square mould, and then cut into small panes.
One of the panes would have been where the blow pipe had been attached, and consequently would have had a series of concentric circles as a result. This was called a 'bullseye'. These can sometimes be seen on ancient glass windows.
I was told that central area of a target was named after this. although why the imperfection in glass was called bullseye I've no idea!
because when the bull see,s red he atackes.