It really wasn't. Getting Santana two years after his album came out isn't really calculated.
Two years isn't a long time, especially considering how big the album was. Sold 30 million worldwide, which is tremendous for an album released in 1999, and even broke
Thriller's record for most awards won in a single night at the 2000 Grammy's. Doing a song with Santana two years after
Supernatural is like doing a song with MJ two years after
Thriller; the success of his album was still felt in the industry, so doing a song with him was an easy way to get a hit.
And MJ couldn't have worked with Santana sooner after his album came out, anyway, because he was busy touring to promote it.
Supernatural came out in June 1999; his tour started in February of that year and ended in October 2000. "Whatever Happens" was recorded in February 2001, so MJ basically got Santana as soon as he was available.
And getting him on a song that was made 2 years before that is interesting.
Not really. MJ just took someone else's song and recorded it without adding any of his own input beyond the vocals. The lyrics and melody are basically the same as the demo; MJ slapped his name onto the list of co-writers even though he wrote no part of the song. Neither did Teddy Riley, for that matter; Gil Cang and Geoffrey Williams wrote it all by themselves.
A lot of songs on
Invincible are like this. Dr. Freeze confirmed that he wrote "Break of Dawn" all by himself, the writer demos to "Heaven Can Wait" and "Butterflies" are basically the same as the final versions if I remember correctly (and "Heaven Can Wait" was supposed to be a Blackstreet song before MJ asked Teddy for it), "2000 Watts" was supposed to be for Tyrese on his album of the same name before MJ asked Teddy for it, Darkchild wrote the songs that he produced all by himself with his brother Fred and LaShawn Daniels and the only thing MJ changed on "You Are My Life" was the title from "You Are My World".
Hard to feel like MJ worked hard on this album when he's giving himself co-writer credits on songs he didn't actually write at all. Save for "Speechless" and "The Lost Children", all of the songs were written by other people; MJ would pick them for his album after hearing the demos and just add his own vocals. He was just shopping, basically.