Why was the RIPEMD-160 hash algorithms chosen before SHA-1?
There are a multitude of reasons.

As @ThePiachu mentioned, there is a theoretical 2^60 bit attack that is possible on SHA-1, meaning that the algorithm is weaker than designed.

RIPEMD-160 was designed in the open academic community, in contrast to the NSA designed SHA-1 and SHA-2 algorithms.
It is worth noting that Satoshi could've used SHA2-256 twice and truncated the second digest to 160 bits as this is equally secure. The fact that he didn't is some evidence to show that his decision was a conscious decision to use RIPEMD-160 over the NSA suit of algorithms.

Lastly, I believe RIPEMD is based on a different design to the SHA1/SHA2 algorithms, and thus attacks that apply to one may not be transferable to the other (which is good).