Final answer:
Robert Bly significantly influenced the haikai movement by giving it a distinctive prose style that mirrors societal evolution from sacred culture to democracy and felt particularly free in composing prose poems due to the lack of established standards at the time.
Step-by-step explanation:
Robert Bly played a critical role in giving the haikai movement a distinctive prose style. In a 1997 interview, Bly connected the evolution of this poetic form to the broader evolution in human society—from a sacred culture to aristocracy, to democracy. He described the progression from sacred chants to metrical poetry, then to free verse and prose, mirroring this societal progression.
Bly felt a particular freedom and "safety" in writing prose poems, as there were no established standards constraining their creation at the time. This innovative approach is part of what has shaped the modern understanding and practice of haikai, a variant of haiku that often includes a formal prose component in addition to traditional structured poetry.