How can predicting protein folding speed up drug discovery?
Firstly protein structures are not infinite. Most proteins adopt specific structure.
Drugs carry out their function by binding to its target protein. Structure prediction helps drug discovery process in two ways -

it allows identification of pockets in target proteins (where drugs can bind) whose structures are not yet solved using experimental methods
it allows in silico experimentation i.e. you can take a large number of molecules and simulate whether they will bind to a specific location in your target

I would suggest going through these reviews to get a better overview of the importance of fast and accurate structure determination in drug discovery :

Verinde and Hol, 1994, Structure
Montfort and Workman, 2017, Essays in Biochemistry