Firstly, it was a solidly booked show, add in the factors of:
- The fact it was a post-Wrestlemania crowd who was pretty excited to be there in the first place
- The Rock unexpectedly beating Cena and then cutting a promo promising he would be champion had the crowd going too.
- Bryan losing to Sheamus so quickly at WM had the crowd showing support for the rest of the night and bled into the next night too. They would have been really anticipating his appearance.
- The rumours of Lesnar coming back were strong and people were buzzing for that. There were a few chants for him throughout the night. When his music hit, it was amazing.
So yeah, a few factors there that had the crowd very excited throughout the whole show. As others said, probably not the best ever, but they were certainly fantastic.