Why is the phylum Arthropoda the largest phylum in the animal kingdom?

why is the phylum Arthropoda the largest phylum in the animal kingdom?

Phylum Arthropoda has almost a million species described to date. It accounts for 80% of known animal species. So phylum Arthropoda is the largest phylum in the animal kingdom. Several factors contributed to the success of arthropods especially the terrestrial arthropods as they adapted to solve the problems of support, stability, desiccation and respiration.