Why is the prime minister voted by the Government team and not the citizens of Australia?
Role of the Prime Minister in Australia.

Parliamentary Education Office (peo.gov.au)
Description
This graphic shows that the Prime Minister is the most senior minister in the Australian Government as well as being key spokesperson for Australia, the head of Cabinet and the leader of the government.
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The leader of the political party or parties with the support of the majority of members in the House of Representatives becomes the prime minister. They are either chosen by the parliamentary members or their party or all the members of the political party.
This way of chosing the prime minister is a convention – tradition – that comes from the British Parliament. Another convention in the Australian Parliament is that the Prime Minister is always a member of the House of Representatives, not a senator.