There are a variety of synonyms one could use in place of "flabbergast the people." Some options might include "amaze," "astound," "dumbfound," "stun," "bewilder," or "startle." Each of these words carries a slightly different connotation, but all describe a state of shock or surprise. Depending on the context and intended audience, one synonym may be more appropriate than the others; for example, "amaze" might be a better choice for a younger audience, while "bewilder" could be more appropriate for a more mature or intellectual audience. Regardless, all of these words convey a sense of shock and awe, making them effective tools for describing remarkable or unexpected events.