In these big races, transition zones are *huge*. Running through them without all the gear swaps takes time. Still:

swim-bike: strip wetsuit (sometimes); cap off; goggles off; run to bike/tent; socks on; shoes on; helmet on; gloves on (sometimes); shades on; get bike; run it out of the transition zone and go. Yeah, 3 minutes is miraculously fast in a big Ironman.

bike-run is a little easier - run bike back to rack; helmet off; gloves off; shoes off; shoes on; hat on (sometimes); run out of transition zone; go.

My mom's last tri (in her late 70s) was at the age-group Worlds - sprint distance. Her knees were already giving out, but she was holding out on replacing them until after the race. She knew she had 5km in them. She did *not* have 5km + 2x monster transition zones. But she toughed it out and was the fastest old broad in the world that year :) :) :)