We dive into the catastrophic organizational failures of the SHA-1 to SHA-2 migration, revealing why enterprises missed hidden certificates and suffered dependency shock. This historical scramble offers urgent lessons for the PQC transition. Learn how the "Harvest Now, Decrypt Later" (HNDL) threat necessitates immediate action, necessitating C-suite leadership, extensive PKI overhauls, and mandatory crypto-agility to counter quantum computers and meet the non-negotiable 2031 deadlines.