Why do public keys for RSASSA-PKCS1-v1_5 follow a normal distribution? I converted ~1000 public keys generated from chrome's RSASSA-PKCS1-v1_5 implementation, converted them to decimal, prepended a "0." to them, and sorted them. 

This is the graph that I got:



It puzzled me a little bit because it looks like an inverse normal distribution. I expected a uniform distribution (i.e. straight line). what gives?

the datapoints are the actual values of the keys, you could say normalized 0 to max, sorted, and then plotted by index in the sorted array.
It's not perfectly clear what your graph is actually displaying.

However, if you expect that $k$-bit RSA keys are equidistributed between $2^{k-1}$ and $2^k$, well, that's not likely (unless the key generator goes out of its way to try to ensure that).

Remember, an RSA key is (usually) produced by independently selecting two primes from a range of $[c2^{k/2}, 2^{k/2}]$ (where common values of $c$ are $0.75$ and $\sqrt{1/2} \approx 0.7071$; it varies between implementations; I don't know what Chrome uses).

Each prime might be approximately equidistributed, but the product of two such primes will be somewhat closer to a normal distribution, with intermediate values being of higher probability; however note that it won't really be that close to normal.