they really were.后面的表语就是as前面说的一句话所表明的状态,因此这里需要as连接,这种句式的目的是强调were后面的这个事实情况,即as前面的的一句话所表明的观点；
如：they were fast as they really were.意思即为：他们确实很快.如果不要as后面的一段话,they were fast意思就是,他们很快.缺少强调的语气.而这里,as they really were后面的表语既是前面这句话“they were fast”所表明的状态,突出强调语气.