philosophy was science in old era in western civilization

I would say rather that there was a split between philosophy and science in the 16th-century scientific revolution. Previously, the role of philosophy (especially natural philosophy, the precursor to science) was to offer meaningful explanations for the universe, using empirical observations to justify the explanations. After the scientific revolution, the role of the new discipline of science was to look for patterns and laws in the universe, whether or not there were meaningful explanations for them. Philosophy took more of a back seat, still looking for meaning in the patterns revealed by science but without steering science in the process.