Do we need a conjunction in this sentence?

The following Passage has been taken from a website. This example shows how repeated terms should be used in sentences.

The Swiss watchmakers' failure to capitalize on the invention of the digital timepiece was both astonishing and alarming — astonishing in that the Swiss had, since the beginnings of the industrial revolution in Europe, been among the first to capitalize on technical innovations, alarming in that a tremendous industrial potential had been lost to their chief competitors, the watchmakers of Japan.

Can we put a conjunction in the above sentences instead of a comma. Which one of the sentences is better/preffered; sentence with conjunction or without conjunction?

The Swiss watchmakers' failure to capitalize on the invention of the digital timepiece was both astonishing and alarming — astonishing in that the Swiss had, since the beginnings of the industrial revolution in Europe, been among the first to capitalize on technical innovations and alarming in that a tremendous industrial potential had been lost to their chief competitors, the watchmakers of Japan.

GB