What da faq! But why & how?

Because human beings as a species are inherently extravagant and dim-witted, and ultimately doomed as a whole because we can't pull our shit together

https://www.reddit.com/r/explainlikeimfive/comments/l7nx0/eli5_the_implication_of_cancelling_all_world_debt/c2qftxo
This is an excellent explanation of what debt really is.
tldr: debt=money

The planet is in debt by the banks the big (mostly private) Banks. Like the Federal Reserve Bank or the European Central Bank

Eachother

I'm gonna guess we owe this to future generations. But, yeah, let's run it up more.