There were many different turning points during the Armada, you can explore them all in more detail. This site was made after I had a school project on the subject and a noticed that there were no sites about why it failed so ... here it is! If you want details of what happened check out the links and search the web there are many good sites.
- Was it ever going to succeed- was it a bad plan?
- Did Medina Sidonia poorly lead the Armada?
- Did the English attack at Calais cause the Spanish to fail their objectives?
- Was it the English victory at the Battle of Gravelines that caused the table to turn?
- Were the English Ships Superior?
- Did fortune just favour the English / Were the English in the right place at the right time?