The following is a video of an excellent talk by Professor John Semple on why ITP occurs.
It was from a presentation made to the ITP Support Association annual convention held online in May 2021.
In my 16 years of living with ITP it is the best explanation of why it occurs and not only is it interesting and helpful but it is quite easy to follow for the layperson.
Here is the link - youtu.be/3rCz_fQkxxA