Being is used as causal clause equivalent. It gives the reason why Horace Pippin worked the way he worked. Because Horace Pippin's right hand and arm were/had been crippled by a sniper's bullit during the First World War , he worked by holding the brush in his right hand and guiding its movements with his left.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.