Why do hyper-active trial users sometimes vanish right before paying?

We learned this the hard way after watching people spend hours setting up complex dashboards inviting team members and clicking every single button during their trial only to ghost us on day 14.

Meanwhile, a few quiet users who logged in twice, set up one core thing, and stayed silent ended up converting with zero hesitation. Activity volume doesn't always equal real intent.

If high usage isn't a reliable sign of a buyer what specific milestone or action do you actually look for during a trial?