Innocent lll was the most successful pope in the high middle ages because he?

I'd argue it's because he wielded diplomacy based on core Catholic Church values and refused to capitulate to the notions of divine right of kings. He staunchly defended papal power, so (a) is correct. He successfully disciplined kings and heretics and encouraged innovation, so (b) is correct. the other two, not so much. Look when he motivated Henry IV to trudge through the snow and lay prostrate in the freezing weather outside the castle walls begging for forgiveness, begging the pope to hear his confession and allow him to receive Eucharist again, THAT was the power of Jesus Christ acting through the Vicar of Christ. It was a shining moment, but look at what would happen from within the Church just a few centuries later in Wittenberg. The technology of the printing press wasn't around for use, and weak priests could not be co-opted so easily in Innocent III's day. Oh those German princes.... Investiture was a harsh era, and Innocent III was the right man for the times.