2008-2009 was the preparation. The first 2 years she upped the game and made pop take on deeper artistry/imagery. Before Gaga, people were just dilly dallying doing their thing, for half a ****ing decade besides Beyoncé with Single Ladies. Before that, Britney was the only pop girl to make her mark. The only truly iconic aspect of that last decade was Single Ladies and Britney's downfall, and I don't think The Fame would have happened otherwise. The destruction of the blonde superstar was about Britney.
Gaga inspired pop culture too much to the point of oversaturation. She set waves throughout pop culture which all the girls rode, and some got lost in the riptide (Miley Cyrus). They had to end up doing the complete opposite, which is truly sad, because Gaga had to give up who she truly was to stay relevant, despite her force in pop culture.