Because he was himself while adapting to the trends.
This right here.
And it wasn't just females who liked him either. Most legends have LL in their Top 5. KRS, Fat Joe, G Rap, Dr. Dre, Kane, EPMD, Twista, B.I.G., Scarface, Nas, Keith Murray, Treach, 50, and the list goes on and on. Legends love LL. So when you have so many people that throw you in their Top 5 and always show you respect and love, and you're constantly able to make classic records with the newer artists ("Who Shot Ya (Remix)", "Flava In Ya Ear (Remix), "Rampage" and "4,3,2,1"), you don’t have to worry about being out of touch. He was always right there with the new MC's, still selling mad records and making dope sh*t.
Derek Jeter said "Headsprung" gets him focused on the game, so that became his come-out music for a minute at the Yankee home games. At that point, LL had already been in the game for 20 years and was on his 10th album! And dude was still selling almost like 200,000 physical copies first week, which was more than he had ever before first week, on any of his other albums. Dude is Hip Hop's first superstar, and his career shows why.