In the Lion King, the Hyenas were an alternate pack with loyalty to Scar, Mufasa's (the previous king) brother. The Pridelands of the lions suffered greatly for everyone after Scar ascended to power through murdering his brother with a stampede induced with the hyenas backing, and running off Mufasa's son through psychological manipulation, clearing the way for his own ascension to the throne.

Ultimately, Scar was undone by the very pack that helped him ascend to power, and everyone lived happily ever after after the return of the rightful King's son, blah blah blah... You get the picture.

Point being, the hyena comment is not terribly flattering in any dimension. It implies both a fundamental weakness of character in terms of being willing to be led by the most degenerate and awful type of person willing to tell one what one wants to hear, and promise to deliver what one wants while simultaneously being ultimately opportunistic in alignment/loyalty, and only rising up/breaking from an inept or cruel charismatic pack leader only on after another external force has done most of the work in making the need to switch apparent.