Because the dist. shaft goes into the intermediate shaft, which has a gear on it. The gear meshes with the cam gear, which turns the cam. The cam timing chain would have to turn the crankshaft, pistons and bearings. Cannot be done safely, if at all.
Remove the Dist. and intermediate shaft. Insert long hex priming tool into oil pump hex. Spin with a low torque drill till you feel resistance. This will fill the oil pump, filter, and passages. Rotating the crank 2 turns will get some oil up to the rockers. Rotating the crank slowly while watching the rockers will fill the rocker shafts.
