Two examples of technique I'm aware of are the Fosbury Flop (1968) in the high jump, in which the jumper goes backwards over the bar (previously jumpers had gone forwards and feet-first, by 1968 with a sissors step), and heads-down technique in Australian Crawl "freestyle" swimming. Both dramatically improved results.
The Fosbury Flop was enabled by the technological introduction of foam mats on the landing side of the high-jump. Without mats, landing on your back after clearing a 2m+ bar position was somewhat undesirable.
Heads-down stroke in freestyle was in conjunction with freshwater (rather than salt) in swimming pools. Swimming heads-down without goggles in a salt-water pool burns the eyes quite strongly. With freshwater, and acrylic plastic goggles (acrylic being invented in the Great Plastics Boom of the 1930s). I'm not entirely sure when plastic swim goggles became widespread, though it may not have been until the 1970s, and the Montreal Olympics (1976) were the first to permit goggles.
Track generally has also seen tremendous improvements in the track composition (loose cinders to rubberised surface). Swimming pools have hugely reduced wave action through wave-absorbing lane lines, deep gutters, inlet diffusers, and laser-guided construction ensuring accurate and consistent distance.
That's on top of vast improvements in training, other equipment, doping (which has a very long history), professionalisation of sport (including the Olympics), and other factors.
Talent is a component, but the overall phenomenon is highly multidimensional.
Various types of doping could cause this too. More positively, tech, diet and science changes could too in some sports too.
