No one gives a fuck about an 18 year old Prince Phillip of Greece and Denmark grooming a 13 year old heir to the British Throne either.
I guess if your da gets away with being a nonce then Andy has thought he may as well give it a go.
The simple fact is, back in those days, it was more common and considered more acceptable. There are people who we still hero worship as rockstars who spent the 1970s sleeping with underage girls. Here is one famous "baby groupie":
https://en.wikipedia.org/wiki/Sable_StarrLost her virginity at 12 to a rock star, slept with Iggy Pop when she was 13, and claimed to have slept with David Bowie, Robert Plant, Jimmy Page, and Johnny Thunders. She was far from the only one.
I remember when I was younger you'd have 15 year old girls getting picked up outside of school (still in their uniforms) by lads in their 20s with cars. That was only 20 years ago. I remember getting to my 20s and thinking "why the fuck would you want to sleep with a 16 year old, let alone someone younger?!". Grim.
None of this is a defence of Prince Andrew by the way. Just pointing out how much our ideas of consent, safeguarding and sexual assault have changed.