What do you mean "all media called Gore the winner"? I can't find any evidence of that. According to Wikipedia [1], "on November 8 ... the networks declared that Bush had carried Florida and therefore been elected president. ... after all votes were counted, ... the networks retracted their declarations that Bush had won Florida and the presidency".

Also, note that Gore privately conceded the election that night, but retracted it after further counting due to the <1000 vote margin.

So in fact major networks (including CNN, ABC, FOX) initially called Bush the winner, but retracted that afterwards due to the possibility of a recount.

[1] https://en.wikipedia.org/wiki/2000_United_States_presidentia...