How much are the accelerators? something tells me more expensive than delivering comparable throughput, highly flexible off the shelf x86 hardware.
Looks a lot now, but back then you didn't have server CPUs with gazillion cores on the cheap.
It was also about getting more bandwidth to a single server. 20Gb/s was a practical limit per mainstream server, but with accelerators you could've multiplied it many times more than the fastest CPU on the market.
You also didn't have the AES instruction set to improve the SSL performance.