You are getting it wrong OP. Michael Jackson didn't die poor despite the debt that he is owing. Michael Jackson has a multi million dollar estate which he built and up till date, that property is still generating massive income which his three kids are getting their own share from that investment based on the percentage given to them. Michael Jackson asset that he left enough to take of his children and their children children.
And don't forget that MJ was an artist so his work will continue to generate income even after he passed away. MJ received a portion of his income from royalties, publishing rights, merchandise and other sources. I've heard that thanks to the careful management of his will the total value of his estate is currently estimated to exceed $2 billion by 2025 for his surviving family.