Well, I think he was mainly an opportunist.
But for a solid 20 years, he spoke and acted in socialist terms, as socialism is the best means to control the citizenry and consolidate power, which is what he needed for his Reich. Some quotes:
"We are socialists, we are enemies of today’s capitalistic economic system for the exploitation of the economically weak, with its unfair salaries, with its unseemly evaluation of a human being according to wealth and property instead of responsibility and performance, and we are all determined to destroy this system under all conditions”
[I desire to] “convert the German people to socialism without simply killing off the old individualists”
And my personal favorite, taken to heart by ANTIFA and the “One Percent” (aka “Jews” movement):
"If we are socialists, then we must definitely be anti-semites – and the opposite, in that case, is Materialism and Mammonism, which we seek to oppose.” “How, as a socialist, can you not be an anti-semite?”
Regarding why he left his cronies in charge of industry (or kicked the owners out and put his cronies in): “Why need we trouble to socialize banks and factories? We socialize human beings.”
And some bits from the Nazi Party platform sound familiar (not to mention 100% socialized healthcare, banning guns (which failed, so he just took guns from Jews), and giant make-work projects like the Autobahn:
That all unearned income [aka interest, profit, dividends], and all income that does not arise from work, be abolished.
Since every war imposes on the people fearful sacrifices in blood and treasure, all personal profit arising from the war must be regarded as treason to the people. We therefore demand the total confiscation of all war profits.
We demand the nationalization of all trusts (the means of inheritance in Germany – so a 100% death tax in most cases).
We demand profit-sharing in large industries (Bernie would be proud!).
We demand a generous increase in old-age pensions.
- In order to carry out this program we demand: the creation of a strong central authority in the State, the unconditional authority by the political central parliament of the whole State and all its organizations.
The formation of professional committees and of committees representing the several estates of the realm, to ensure that the laws promulgated by the central authority shall be carried out by the federal states.
The leaders of the party undertake to promote the execution of the foregoing points at all costs, if necessary at the sacrifice of their own lives
Now, was he really a true believer socialist? Meh, probably not.
It was probably just B.S. plied on the masses to get them to create a system where he and his cronies had complete control.
But, then again, that’s all any socialism talk is – B.S. for the useful idiots to lap up in order to create a system so a certain group (whatever said group is) can have complete control, be it Hitler, or Hugo Chavez, or Hillary Clinton.
So, when recognizing that socialism is always just a scam, yes, then, Hitler was a socialist.