This may be the real reason they resigned. A career person does not resign unless their pension is fully locked in. And maybe their pensions are locked in due to years of service.
By leaving they cannot be asked questions about past actions or events and be expected to answer as part of their employment. Refusing to answer (or taking the 5th) while still employed would cast them in a poor light while any answer given could give rise to further more zero'd in questions.
While they cannot work as a lobyist they can be highly paid by those who actually have been pulling the State Dept's strings. In that way they can further the original goals, make use of their contacts and be used to counter any change in direction by Trump.
Trump promised to drain the swamp, and one of the most swampy areas has been in the Department of State. These top officials have made big bucks off the backs of the tax payers to go out and do some pretty questionable things. The United States is better off without them.
The fact that the State Department's top management team resigned is not bad for America. In fact, most Americans were probably unaware that the State Department even has a management team. Our foreign policy has been a mess over the past several years - these departures really won't make things worse.
No, the resignation of top State Department Officials is not necessarily a bad thing for America. Officials resign all the time and are replaced--hopefully by qualified individuals. This resignation is more of a symptom. It shows there are serious problems in the U.S. government right now and that they could cause problems with the rest of the world.