Simplify the following text for a Grade 13 native English-speaking person.
Original: Mandelstam 's non-conformist , anti-establishment tendencies were not heavily disguised .
Simplified: Mandelstam 's non-conformist , anti-establishment tendencies always simmered not far from the surface , and in the autumn of 1933 they broke through in form of the famous `` Stalin Epigram '' .