Python/Ruby/PHP/Javascript are easier to learn because most people already know a similar language. Just because it seems unfair doesn't mean it's not true.
Python and Ruby do one particular thing right that Smalltalk didn't:
Operator Precedence for Algebras.
Implementing an Algebra is a very important thing for a language to be good at. Being able to use algebras without having to switch mental gears is a good thing for scientists, mathematicians, and technical people of all stripes.
IMHO, the ability to easily implement your own algebra is a hallmark of a great language. Having that with the operator precedence is a bit of very justified syntactic sugar.
