At the time of his 3 prior KOs Wlad was not considered the king of the heavyweight boxing division.
There also has been a drought of dominant heavyweights in boxing.
The heavyweight division is just one young champ with power away from being a part of the general public's consciousness. People in this country only stopped caring about heavyweight boxing because it has been owned by foreigners for too long.
Wilder would be seen as the savior of boxing who brought dominance of the heavyweight division back to the US.
So I will repeat once again because you seem to not be grasping it: if Wilder were to stay undefeated (KOing people along the way) and unify the heavyweight title by dominating Wlad he would automatically become the biggest star in boxing because the US public has always preferred the heavyweight division as long as their has been US fighters at the highest levels fighting in that division.
Wilder could reign the heavyweight division his entire career, he still won't be Floyd's level, he's just not that type of guy
if Lennox Lewis could reach Tyson levels of popularity what the hell makes you think Wilder will