It is faster to process a sorted array than an unsorted array because of Branch Prediction.
Now, branch prediction means determining whether a conditional branch in a program is gonna run or not. As the array is sorted, Predicting the Reaction of elements for a particular conditional Statement becomes Easy.
For example -
Consider you have a list of number which are sorted, you pick the first number and it is 3, the next is 5 and so on... , after the second number you can easily predict that all the next number will be greater than 5. Whereas, such a Prediction is not possible in an Unsorted Array.