The Basilica has not a smaller capacity than the Square. Just compare a football stadium with the square and you will see that this article has the truth - 30,000 fill St Peter's Square
http://www.heraldsun.news.com.au/common/story_page/0,5478,12729544%255E1702,00.html
The capacity of the Basilica is 60,000.
The capacity of the Square is 300,000
A search of articles give the 300,000 for many previous events held in the Piazza, so this isn't just a recently invented number.
You are EXTREMELY confused.
(post repeated on other thread)