"Normans' ambition was to make of England a trilingual country."
What is the meaning of phrasal verb "make of."
I suspect you mean, "the Normans".
This is an inversion. The standard version would be:
"The Normans' ambition was to make a trilingual country of England."
This can be compared with, "Janet's ambition was to make a teapot of clay."
So Janet wishes to convert clay into a teapot. The Normans want to convert England into a tri-lingual nation.