He is only one man and elderly(if he’s even still alive). The young “hotheads” may very well get their say like they tried to do in 2002 when they set up a ceremonial corner stone by the wailing wall.
The rebuilding of the temple itself isn’t touted by the Bible as a good thing since the temple sacrifices that get restarted are a rejection of the blood sacridice of Jesus Christ for the remission of the sins for all mankind. All references in the Bible to it are neutral. God does get displeased when the beast sets himself up in the temple and calls himself God.
The rabbis who get to decide are actual scholars such as Shalom Cohen, Reuven Elbaz, Gershon Edelstein and Dovid Feinstein.
‘Hotheads’ are just trying to get in on tourist money, or maybe mentally ill.