Reference of "all three"

Can any one understand what the highlighted "all three" refers to in the following context? Does it refer to "the carnival, the grotesque and horror house" or "sheer amazement, shock and embarrassment"?

The artist as clown is clearly articulated in his Painter video and elements of the carnival, the grotesque and horror house permeate his works. McCarthy parodies, satires and mocks with razor-sharp wit, and in Freudian terms McCarthy releases repressed aggression through humour, although crude and perhaps disconcerting. Yet, it is the
distance created through the act of creating the performance where the darkness can come to light in a zone of safety for both performer and audience. The audience may laugh out of sheer amazement, shock and embarrassment at the display of such vulgarity and lack of ‘good taste’ expected from art. They may also laugh because they feel superior to witnessing such pathetic, pathological behaviour, or they may laugh because all three are reasons to release the tension experienced when viewing McCarthy’s works. McCarthy’s works are a good example of Morreall’s theory of laughter; that we may experience incongruities and laugh from viewing McCarthy’s work, but we may not, depending on the viewer, of course, experience pleasure.

https://books.google.nl/books?id=HFhgwLI79tgC&pg=PA95&lpg=PA95&dq=%22because+all+three+are+reasons+to+release+the+tension+experienced+when+viewing%22&source=bl&ots=mnBUCYoOjj&sig=7dY9_TOOm2N7Vi6A9x8Fibl0O5c&hl=en&sa=X&redir_esc=y#v=onepage&q=%22because%20all%20three%20are%20reasons%20to%20release%20the%20tension%20experienced%20when%20viewing%22&f=false