The new and improved grommet was made of..

.. steel!  In 1856, inventor Bessmer applied new technology to the teeny rings.  By this time, women were trusting the metal grommet, and were open and willing to try a new type of metal.

(Featured the new steel grommet on an extant corset.  Below, a late Regency/early Victorian corded instead of boned “light” corset with old fashioned shoulders and early metal grommets – the shoulder straps and light boning would die quickly in the late 1850’s)