The people who win Kaggle competitions are consistently machine learning experts, not domain experts.

Notably: https://www.kaggle.com/c/MerckActivity

> Since our goal was to demonstrate the power of our models, we did no feature engineering and only minimal preprocessing. The only preprocessing we did was occasionally, for some models, to log-transform each individual input feature/covariate. Whenever possible, we prefer to learn features rather than engineer them. This preference probably gives us a disadvantage relative to other Kaggle competitors who have more practice doing effective feature engineering. In this case, however, it worked out well.

http://blog.kaggle.com/2012/11/01/deep-learning-how-i-did-it...

> Q: Do you have any prior experience or domain knowledge that helped you succeed in this competition? A: In fact, no. It was a very good opportunity to learn about image processing.

http://blog.kaggle.com/2016/09/15/draper-satellite-image-chr...

> Do you have any prior experience or domain knowledge that helped you succeed in this competition? I didn't have any knowledge about this domain. The topic is quite new and I couldn't find any papers related to this problem, most probably because there are not public datasets.

http://blog.kaggle.com/2015/09/16/icdm-winners-interview-3rd...

> Do you have any prior experience or domain knowledge that helped you succeed in this competition? M: I have worked in companies that sold items that looked like tubes, but nothing really relevant for the competition. J: Well, I have a basic understanding of what a tube is. L: Not a clue. G: No.

http://blog.kaggle.com/2015/09/22/caterpillar-winners-interv...

> We had no domain knowledge, so we could only go on the information provided by the organizers (well honestly that and Wikipedia). It turned out to be enough though. Robert says it cannot happen again, so we’re currently in the process of hiring a marine biologist ;).

http://blog.kaggle.com/2016/01/29/noaa-right-whale-recogniti...

> Through Kaggle and my current job as a research scientist I’ve learnt lots of interesting things about various application domains, but simultaneously I’ve regularly been surprised by how domain expertise often takes a backseat. If enough data is available, it seems that you actually need to know very little about a problem domain to build effective models, nowadays. Of course it still helps to exploit any prior knowledge about the data that you may have (I’ve done some work on taking advantage of rotational symmetry in convnets myself), but it’s not as crucial to getting decent results as it once was.

http://blog.kaggle.com/2016/08/29/from-kaggle-to-google-deep...

> Oh yes. Every time a new competition comes out, the experts say: "We've built a whole industry around this. We know the answers." And after a couple of weeks, they get blown out of the water.

http://www.slate.com/articles/health_and_science/new_scienti...

Competitions have been won without even looking at the data. Data scientists/machine learners are in the business of automating things -- so why should domain knowledge be any different?

Ok, sure it can help, but it is not necessary, and can even hamper your progress: You are searching for where you think the answer is -- thousands are searching everywhere and finding more than you, the expert, can.