So, how did Cohen do with the assignment of winning the hearts and minds of the American people?

Before Cohen testified,  his approval rating was 51%.  After his testimony,  his approval rating fell to 37%  (per The Hill).

A "37% approval rating" simply means that only the radical Democrat base approved,  to the exclusion of most Independents and,  of course,  all of the patriotic nation.  In short,  this explosive testimony did not move the needle at all.