*更新：
刚刚在书上有看到大概有三个原因可是看不太懂，望各位大大开示：
1、The answer is complicated, with one reason being the development of the com
munity of surrounding nations that needed a weak, internally fragment center i
n which they could adjust the shifting balance of their own interests and figh
t their wars.
(这里实在看不懂，他们需要一个很弱的中心让他们能够……？)
2、Another reason was the emperor’s very weakness, which tended to make him a
n effective peacemaker and a sovereign who ruled through fixed law instead of
a despot.
(为何皇帝很弱，所以变成一个和平主义者？)
3、A further reason for the surprising longevity of the Holy Roman Empire was
the principle of the elective kingship. The higher rank of the aristocracy par
ticipated in the institutions and were disposed to support and cooperate with
the sovereign they chose. Every vote they cast in a royal election was a renew
ed vote for the continuation of the empire, and thus it was precisely the prin
ce elector who came to serve as guarantors of its cohesion and permanence.
(这边好像比较能够理解，大概是自己选的皇帝，自己挺？)
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小妹不才，最近正在念德意志地区的历史，不过有点疑问，希望各位大大解惑。
日耳曼在政治上十分分裂，照理说纷争那么多，内忧外患的，神圣罗马帝国到后来也是德
意志自己在玩的，那为什么他可以存在到19世纪才消失呢？
才疏学浅，有哪里不正确的地方，恳请各位指教。