But why did Maria marry Arnold?
She may have genuinely fallen in love with him, #1Kf.
I could theorize that she went for a conservative immigrant with no pedigree in order to rebel against and embarrass her very, very, very (Did I say very?) liberal family.
However, there is no evidence of that as she has stood by her rather liberal views even after they married.
Also, from everything I heard on the matter, her mother really, really liked Arnold a lot.