The phrase "the bottom line" has its origin in the field of accountancy (BrE) or accounting (AmE). In a firm's financial statements the last line in the statement of income (or profit and loss) is "net income (or profit) for the year". So the phrase "the bottom line" came to mean the only real and important result of something: when you strip away all the superfluous verbiage and bullsh*t, what remains is the bottom line. That was the original meaning.
But your example shows that the meaning of bottom line has probably moved on from its origin. Evidently some people are now using it to mean any authoritative conclusion. Otherwise, how could the author contemplate the existence of more than one bottom line? And how could the concept be applied to something so exceedingly remote as the theatre of the absurd?
Another possibility is that the author is simply pointing out the extreme incompatibility between the concepts of bottom line and theatre of the absurd.
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