When you see the waterfall continuing to run even after finding an email, it's because the email that was found by an earlier data provider failed the validation check. The waterfall continues searching through other providers to ensure you get the highest quality, validated email possible. While these validation columns aren't shown by default to keep your table clean, they're working behind the scenes to verify each email that's found.
Source:Enrich People (Waterfalls) [Automated Inbound] - Clay University