Is it necessary to prepare a Power Point presentation for a 30-minute postdoc interview?
This could depend a bit on the field, of course. But I find powerpoint to be mostly very badly used. Someone once described the typical PP deck as the speaker's notes that shouldn't be shown to the audience. If that is what you tend to do - show a slide and then just repeat a longer form of that orally, then I wouldn't bother. 

There are some people who are truly gifted in the use of PP, but not everyone is. You don't want to be boring. 

But prepare the deck and, at least use it for your own notes while speaking. Depending on the field there may be other, more important, visuals you can use. Even a whiteboard. 

And, given that it will be remote, you could prepare a deck and send it to them for possible distribution and then do something else rather than just show it during the presentation. 

If there is a two way communication system (audio - video) where you can ask and answer questions it would certainly be better than just a lecture-like presentation. I suspect very few people will take notes on your actual content and will be interested in other things. Some students might, but not future colleagues. 

And try to present it to a friend or colleague before you 'go live' to get some feedback and to be sure of the timing. I'd suggest a bit too short is better than one that is too long. Leave them wanting more, not exhausted. 

But in an orthogonal vein, make sure you understand who the audience is. Researchers? Students? Graduate or undergraduate.