This was all happening in plain sight. It was very common for rock stars and any famous men, to have young girls queuing up to meet them. Teenagers were seen as more grown up then. It was common to leave school at fifteen or sixteen and to be married with a kid at 19. I know this, because I was brought up in the 70s.
Jimmy Page wasn't grooming kids outside school gates, teenage girls were throwing themselves at him. My BIL is in a band and one of his bandmates is in a wheelchair and pulls young women every night because he's in a band.
There were 'groupies' who were groups of girls and young women, who would follow bands around and stand outside their hotels waiting to be asked in. I was going to gigs at the age of 12 and 13 years old with friends and drinking in pubs. That would be unheard of now.
That was the kind of atmosphere in the BBC at the time that Saville and other famous (huge household names) DJs were having sex with groupies. People turned a blind eye because it was so common. I don't know about Jimmy Page keeping 13 years olds locked up; sounds sick but it puts that era into context.