Of course her songs have meaning, but that never goes beyond sex or dancing. Feel free to PM me this 50,000 word essay trying to prove otherwise, but the fact remains, all her hits have been pointless, meaningless, yet catchy songs. Her videos rarely have anything to do with the song, look at Telephone and Bad Romance.
The lyrics didn't matter, she could've been singing about pancakes, the songs are catchy and the majority of the buying public won't be looking for anything with meaning, they just want to get trashed and have a dance.
She didn't burst onto the scene either, she fought her way onto the scene and only managed a hit 6 months after she released her single through association with Xtina, her outfits and lack of competition at the time. She didn't make electro current either, here in the UK we've always been that way, over in the US things were moving that way (see the Blackeyed Peas, Kanye West). Britney's Blackout is arguably what set it off, although she'd started back with In The Zone but she was the only one really doing it at that time.
She found a formula that works. Everything is calculated to the "T", extremely contrived, from her persona, to her music, to her videos. She basically keeps writing the same song and releasing it over and over again. She's interesting at the moment, but the next innovator/pop royalty/trendsetter/influence, I don't think so. As I said, once she does something truley artistic and innovative MUSIC wise, she is nothing but a radio wet dream.