That's how things work.
God has to hide behind because humans need faith to be saved in accordance to a covenant between God and men. If God shows up to humans, then humans are no longer savable. Faith only works when God is hiding behind from humans.
However, if God doesn't show up completely humans have no way to know what God wants from us. We can't even know what a covenant is. The only way which works is for God to choose His witnesses and for them to write down their testimonies and what God wants from humans and for the rest of human kind in history to choose to believe with faith.
As a result, God's Law only allows God to select a limited number of direct eyewitnesses (i.e., His prophets) to serve the above purpose. More likely these prophets are predefined before the creation. More often, these prophets can only be saved by means of this anointment as the last resort. That is, it's possible that they are saved simply because they are the pre-selected. Typical examples include David and Paul (a prophet given the ranking of apostle), a murderer and a self-righteous Pharisee persecuted the Christians.
A prophet is thus reckoned along the path before they are born, through the childhood till they are formally anointed. Part of the reason they can self verify themselves as the prophets because God keeps burying marks ever since before their birth and along their childhood. It's more like saying that "you are a selected prophet because I keep marking you so from before your birth and till after". Possibly that's why Paul said that he has the mark of Jesus.
To put it another way, if you declare yourself a prophet then you must have something as a sign or marking buried before your birth or early childhood. God will remind you this when you are formally anointed.
By the same Law of God, God can pre-select a people as His witness as well, which is Israel (the Jews). My advocate here is that this could be the way how Israel as a whole can be saved (of course excluding those wicked in God's eyes), just as prophesied in the Bible.