The type of quants talked about in this article probably has a PhD in math, stats, CS (with a focus on machine learning), or something similar.

This particular article is about MFE students from one school, but hedge funds love PhDs too.

and especially physics, since financial modeling is based on physical modeling.

Well not directly, it's just that they both make use of stochastic calculus.

Any good MOOCs, etc for the topic?

One way to get interviews at least is by doing well in math contests.