Re: only 71? bah!
I ain't Spartacus,
You are entirely correct to point out the assumption of, if not the out right seizure of, dictatorial powers by von Hindenburg and Ludendorff in 1916.
The only mitigation I can see at this distance, is an apparently complete absence of any desire for self-aggrandisment, i.e. the military dictatorship was for the benefit of Germany, not for his own benefit.
Ludendorff's motives, especially in light of his post war behavior, seem, at first glance, much more murky, although I am probably doing him a disservice vis-à-vis his actions in 1916.
There seems to be no dispute by scholars of the period that von Hindenburg disliked and distrusted Hitler from their first meeting, and no change in these views has come to light in all the years since then. There also seems to be a consensus that he was suffering from periods of dementia by 1932, if not somewhat earlier.
It is a matter of record that he was reluctant to serve a second term as President, and was only persuaded to do so on the grounds that he was the only man in Germany who could defeat Hitler.
His repeated refusal to appoint Hitler to the Chancellorship is also a matter of record, and the fact that he finally did so in January of 1933, speaks to me, at least, of senility, rather than a change of heart. We may never know the real story.
I will not suggest that von Hindenburg's was a stainless life, I don't possess any knowledge that would lead me to think so. Nonetheless, it seems to me to be a sad endcap to a life spent in the service of his country.
As Lester says, it will be discussed and debated for a long time to come.
I ain't Spartacus, it has been a pleasure to have this "discussion" with you, perhaps some day we'll have the chance to enjoy a pint or two.