Pentecost is significant because our current PM identifies as ‘pentecostal’.
The festival (as Shavuot) seems to start as a midsummer harvest festival, celebrating the wheat harvest in Israel (Exodus 34:22). But after 70 AD/CE it becomes the celebration of the giving of the Torah (to Moses, as the ‘Ten Commandments’, on Mount Sinai – long story – the Charlton Heston version has nice animation of God’s handwriting).
It metamorphosises again, when the Christians take it over, in Luke, in Acts ch. 2, when it becomes the celebration of the reception of the Holy Spirit (whatever that is) by the followers of Jesus with ‘a sound like the rush of a violent wind’ and the appearance of ‘tongues, as of fire’, when the members of the cult ‘began to speak in other languages’.
The Biblical text is quite explicit that what the devotees were saying was understandable in a number of languages – and there is a specific list of them.
That’s the few thousand years background to what Scomo does on Sundays, which is that, in the slightly adapted wording of Wikipedia, he accepts Jesus Christ as his personal Lord and Saviour, and believes in the baptism in the Holy Spirit that enables a Christian to live a Spirit-filled and empowered life. This empowerment includes the use of spiritual gifts such as speaking in tongues and divine healing.
By definition it’s not insane, as there are millions of others who believe the same infantile nonsense, but it’s still pretty dotty.