Final answer:
When the Heian court turned its focus to arts and culture, it created a power vacuum that was filled by powerful provincial landowners and the rising samurai class, who armed themselves and provided regional stability, growing in influence and prominence.
Step-by-step explanation:
Impact of the Heian Court's Focus on Arts and Culture on Japan's Political Structure
What happened after the royal court in Heian became more focused on arts and culture instead of running the government of Japan was A) Increased influence of powerful provincial landowners and D) Rise of samurai as a prominent social class. As the Heian court's administration became less effective, regional families began to arm themselves for defense and to advance their agendas. With the weakness of the central government, these families grew in power and influence, reclaiming land and eventually acting as regional warlords. The established warrior families, known as the samurai, emerged as a major force, offering stability and security and thus gaining significant footholds in the political and military arenas of Japan. Through their strength and organization, they rose to prominence and effectively filled the power vacuum left by the ineffective central authority.