I'm not sure I'd called M2Crypto a much better API. It more or less exposes the OpenSSL API which is also notoriously hard to get right. Further more it hasn't seen an update since 2011, the SSL certificate for the bug tracker expired in 2011, and it does not compile without patches against any modern OpenSSL (1.0+).

The state of crypto in Python is horrendous, hence the new library.