One thing that has changed is that their userbase broadened.

They were mostly focused on workplace meetings. If that's your focus, then most of your users are employees of some company whose contact information you have. Users with unverified identities are a corner case that you may not feel is worth trying to get right.

Thanks to the pandemic, they have millions of new users who use Zoom for personal purposes (meeting with friends and family, etc.). What once was a corner case isn't anymore. It might even be their most common type of user.

I'm not arguing that Zoom can necessarily be trusted, but I can see a plausible reason how they could have gotten to where they are on this issue.