Actually the term "Socialist", a trendy marketing term at the time, was already in the name of the party when Hitler joined it. He objected to it but went along for, as you said, its marketing power. And then he organized the "Brownshirts" to attack and intimidate the actual Socialists, and made them the first "guests" at Dachau, while declaring their political party illegal.
Hitler's Economics
[Originally published August 02, 2003.]
[...]
What were those economic policies? He suspended the gold standard, embarked on huge public-works programs like autobahns, protected industry from foreign competition, expanded credit, instituted jobs programs, bullied the private sector on prices and production decisions, vastly expanded the military, enforced capital controls, instituted family planning, penalized smoking, brought about national healthcare and unemployment insurance, imposed education standards, and eventually ran huge deficits. The Nazi interventionist program was essential to the regime's rejection of the market economy and its embrace of socialism in one country.
[my highlight]
Hitler's Economics | Llewellyn H. Rockwell Jr.