Imagine a situation where holders of both sar and Nst either...

Imagine a situation where holders of both sar and Nst either sold short directly or lent out to shorters their Nst shares, safe in the knowledge they would never have to buy back the Nst shares and return to the owner, because by virtue of the merger they were about to receive more Nst shares anyway via their sar holding.
They immediately sell the Nst and wait to pay back in shares, having sold at a much higher price.
Absolutely an arbitrage play and nothing to do with company fundamentals, usual pog caveat applys, I'm holding tight, only bought in recent times tc.