It isn't necessary, but many physicists have to analyze huge amounts of data out of necessity. Telescopes and particle accelerators generate petabytes of data. So they have a lot of practice with this sort of thing. Physicists also have to be ridiculously good at math and particularly statistics, again out of necessity.
Again, physics isn't really a prerequisite. It is just that many physicists have the relevant experience already to be a good data scientist.
Physics is pretty close to data science. In the end, physics often is about applying the scientific method to sth. Traditionally, sth is "the world", but it's not too different if it's just another set of data.
Again, physics isn't really a prerequisite. It is just that many physicists have the relevant experience already to be a good data scientist.