There may be a perfect reasonable explanation - for example any German who worked at Auschwitz is a perfect position to be blackmailed by the Federal Police. Basically gives us a good performance and we guarantee you won't go on trial - otherwise..... And lets face it, they have put plenty of older men on trial for these things.
But I wonder if that is necessarily it.
Is Oskar Groening even his real name, it isn't listed in the telephone book.
According to Lawrence Rees
After the war, Oskar Groening took up a hobby. He worked as a manager in a glass factory near Hamburg, but in his own time he became a keen stamp collector. It was at a meeting of his local philately club, in the late 1980s, that Groenig found himself chatting to a man about politics.
"Isn't it terrible," said the man, "that the government says it's illegal to
say anything against the killing of millions of Jews in Auschwitz?" He went
on to explain to Groening how it was "inconceivable" for so many bodies to have been burned.
Groening said nothing to contradict these statements. But the attempt to deny the reality of Auschwitz, the site of the largest mass murder in history, upset him and made him angry. He obtained one of the Holocaust deniers' pamphlets that his fellow stamp collector had recommended, wrote an ironic commentary on it, and posted it to the man from the philately club.
Suddenly, he started to get phone calls from strangers who disputed his
view. It turned out that his denunciation of the Holocaust deniers' case had been printed in a neo-Nazi magazine. The calls and letters he received "were all from people who tried to prove that Auschwitz was a huge mistake, a big hallucination, because it hadn't happened".
So he was maybe drawing attention to himself in the 80s - or maybe this is simply Rees' fiction. I did ask a couple of friends who work in the Federal Police on these matters if they knew about the neo nazi magazine it appeared in, and if there was a copy still around and they got quite snakey. So maybe this is just a myth propagated to explain how the BBC got hold of him.
It shouldn't be that hard to get hold of his true identity, he was a judge in an employment court and that should be available thru archives.
Some more information is here
Here, Groening is quite explicit about seeing gas chambers (assuming that the interview transcript has not been tampered with - but frankly Mr Groening seems most cooperative that it is unlikely to have been necessary).
However the most revealing quote is:
The interview, said Groening is the "first time in 60 years that I am publicly talking about my time in Auschwitz." Groening was found innocent by a war crimes court in 1948 and testified against numerous other officers in post-war trials. In the interview, he says he has not been back to Auschwitz since the war because he is "ashamed" of what he did there.
Far from being someone seeking to forget his wartime past, he appears to have been a professional witness - that presumably only recently as decided to embellish his account with stories of Auschwitz.
It would be very interesting to know Mr Groening's true identity and what exactly were the war crimes trials he testified at and what he said.