Remember, industrial action is entirely legal with a mandate of a proper adjudicated ballot, which it was.
Was it? I pose this as a genuine question, not a retort. I know nothing about industrial relations or employment law.
I fail to see how "are you prepared to participate in strike action" translates to "are you happy to give us a mandate to call, and ask you to take part in, one of the biggest strikes in the industry's history, at the most inconvenient time for nearly a million people."
I really don't think a lot of people knew what they were voting for.
I am in the process of booking with another airline. It's going to cost me a fortune, and I will take the BA flight if it goes ahead as it's more convenient. But they have just lost my custom for life. As, I suspect, is the case for many.