Because Android is so entrenched, there's no "going back". Google merely paying a fine doesn't change the fact it's still using Java API's moving forwards. Google would have to license the Java API from Oracle... but then who sets the price? Oracle could set something absurdly 1000x higher than reasonable by holding the entire Android ecosystem hostage, no? Would the court decide not just penalties for past usage, but a negotiation for future usage? How would they determine that? (And if they did, couldn't that create a moral hazard? Companies steal IP from someone who refuses to sell, get "too big to fail", and get to keep the stolen IP in the end.)
I'm not familiar with how the law relates to ongoing conflicts that are so massive they can't be undone without great harm to individuals and businesses far beyond the actual parties in dispute.