Pretty normal for any kind of people either irl or online. Most people will jump to another if the work has better manager, rates, rules, estimated uptime of the campaign and etc. disregarding the time of when they applied. In short a job with better benefits.
If they know that the pay is too small, for the first sight, they should not apply for it and they should be patient for next one
The question is when it will be the next one, better to apply on the existing while you are waiting for better one, isn't it?
...you have disorganized the former manager's plan
I don't think so, i bet it's it's easy for them to clear and update the sheet.