Could the crowd see someone on the pinnacle of the temple?
Yes. The temple pinnacle was not as high as modern skyscrapers, so it was no problem for the crowds below to see someone standing on it. The temple crowds were down below, and a person on the pinnacle was easily within their eyesight.
Les explains that Satan took Jesus up into the Holy City and set Him on the pinnacle of the temple, with the temple crowds down below. The pinnacle was not as high as some modern skyscrapers, so it was no problem seeing someone up there—it was easily within eyesight. Satan then proposed a showmanship event, urging Jesus to cast Himself down and have angels catch Him before He hit the ground, which would have amazed the crowd on the temple pavement. Jesus refused, saying it is written, “Thou shalt not tempt the Lord thy God.”