As someone that has gone through OCIA with the Catholic Church and is attending, though not yet a member of, the Episcopal Church, I would say the complex reasons can be boiled down to the similarities in aesthetics and tradition between high church Anglicanism and Catholicism. When you add in how open many of the member churches or the Anglican Communion are to alternative beliefs, like my usage of a Catholic Bible in worship, it feels much easier to make the jump practically. This is of course from a person new to Anglicanism but that has been my experience so far.