If I'm not missing anything, I believe this must have happened because of unusually high levels of fraud on Bitcoin visa cards. Certain acquirers might've complained about abnormal amounts of "shady" volume from WaveCrest BINs.
Alternatively, Visa might have seen a settlement risk on WaveCrest's end. I.e. Visa might be worried that fluctuations in BTCs price would put WaveCrest in a position that they wouldn't be able to settle funds with Visa (and consequently the acquirers + merchants).
Any other ideas on what could've prompted this? I think if this was anti-BTC regulatory action, the prompt to turn off these cards would've come from WaveCrest's banking partners and not Visa.