The simple answer is it's past 90% counted, and what's left of the count offers no path for Trump to win, the numbers don't stack up.
https://results.decisiondeskhq.com/2020/general/arizona
If you click on the "counties" tab there you'll see the count for each, the total count is an estimate, but you can see there are two counties with potentially around 10% left to count, there simply isn't enough outstanding votes, that should Trump win them all to make up the difference. On top of which, the county with the significantly larger number of voters ( 28k ) is leaning 67% to Biden, where as the smaller county ( 7k ) leans 68% Trump. So Trump's likely to win less than half of the remainder at any rate.