In reply to Greasy Prusiks:
I can imagine several reasons for increased maximum performance:
People now sponsored to climb "full time"
Indoor training facilities
Better understanding of training methods and nutrition
Better equipment
Increased media coverage leading to more focus on absolute performance
Increased communication between pros leading to training knowledge/beta sharing
That's just the easy ones, i'm sure there are many small things. The director of British Cycling said something to this effect when talking about the British performance at the 2016 olympics - We have done all the obvious things and now we focus on the many small things, each of which contributes a tiny amount but which add up overall.
Post edited at 16:24