If Zoom made clear to users that connections were not secured to the same standards as competitors, and that potentially hundreds of employees could be silently listening in on any call, I think that would have prevented them becoming a leader in video conference tech. So the right fine here is their entire market cap. That would put them back at square one, which is where an honest competitor would be right now.
Not defending them in any way - but don't think security was the primary reason for Zoom taking off. It was stability - it just worked and at the same time competitors didn't. Everybody used to have Skype and I would have gladly handed over my data to MS if only it would have been able to do stable video calls. It was often a disaster for just 2-way calls, let alone group.
Stability was the main draw, but company IT departments would have had more power to ban it if there were bigger and clearer risks of corporate secrets escaping.