To those who say that 40,000 is not a large number, I will ask a question. How many events in the history of Klal Yisroel (in America at least) have sold 40,000 tickets for one single location? The number is exactly Zero!!
The Siyum Hashas was scattered all over NY/NJ last time. (Continenetal Arena in NJ, MSG and Felt Forum in NYC) Even this time, it has been marketing for YEARS and selling tickets for MONTHS to a national audience of men, women, and children. It is a feel good event, that sells itself to large segments of Daf Yomi participants all across the fruited plain. And they are holding between 40-50K sold so far, if I hear correctly.
This on the other hand, is gonna be a large mussar schmooz, which people don’t like to listen to if they can avoid it (see today’s daf, Tamid 28a, for a lesson about that). It has been publicized for a couple of months, tickets have been available for about a week and a half now. No women or bochurim under age 19 are invited. AND THEY’RE SOLD OUT!!! That is hugely impressive, and a tribute to the respect that many have for America’s Mashgiach.