Although NSDAP government was in general largely opposed to the free-market economy in principle and in practice, as I presented it in this response in the different subreddit, it does not mean that industrialists were persecuted in the Third Reich on account of being industrialists or capitalists (I'm using the term 'capitalist' in its contemporary sense, i.e. a person with a large amount of capital invested in the means of production), as exemplified by e.g. Friedrich Flick, another German industrial magnate who supported NSDAP through until the end of the war and was subsequently tried during the Nuremberg Trials.

To summarize the Nazi's stance on the capital and property, they were generally not opposed to the freedom of enterprise as such, provided it benefited the nation and the state directly, meaning that they were strongly opposed to any form international financial or industrial organizations they considered as disruptive to the national state as communism if not more.

Friedrich Thyssen, whose wealth and industrial empire long predated NSDAP's rise to power, as he was born in the family of an already successful mining and ironworking magnate and becoming a director of the Vereinigte Stahlwerke AG (United Steelworks, PLC) in 1926, has been a long-time supporter of German nationalist parties and was largely considered a hero due to his efforts to incite workers against working for the France and Belgium that occupied Ruhrgebiet (Ruhr Region) in the wake of the Great War, at a substantial personal cost. In addition to his strong patriotic and nationalistic tendencies, being an powerful industrialist, he was also ill-disposed towards all forms of communism or even more radical forms of socialism that proposed partial or total nationalization of the largest companies (and VS AG would most definitely quality, as in late 1920s it employed roughly 210.000 workers and controlled almost 75% of the total German iron ore production. All of this naturally caused his support to gravitate towards nationalist, conservative, anti-communist parties. Initially, his main support was directed at Deutschnationale Volkspartei (German Nationalist People's Party), a conservative-nationalist party with strong monarchic tendencies of which he has been a member, but as it became evident that it will soon be eclipsed by the quickly rising Nationalsozialistische Deutsche Arbeiterpartei (National-Socialist German Workers Party), Thyssen aligned himself with the future leaders of Germany. It is worth noting, that even before he joined NSDAP, he has been supporting it throughout 1920s, considering it a worthy ally due to its both populist and anti-communist character.

In 1932 and 1933 Friedrich Thyssen was deeply involved in the support of NSDAP during the elections, having used his connections with other wealthy industrialists as well as his personal contacts with Hjalmar Schacht, president of the National Bank, and later Minister of Economics in Hitler's government and Paul von Hindenburg, then president of the Republic. This resulted in the large financial support for the party and the pressure to nominate Hitler a Chancellor.

Cooperation between Thyssen and NSDAP was smooth throughout 1930s, with the former offering his unyielding support to the Party as such and the latter reciprocating with the seats in the State Parliament (Reichstag) and the State Council of Prussia. This changed in mid-1935, with the proclamation of the 'Nuremberg Laws' that strongly curtailed already limited liberties of the Jewish citizens of Germany. Thyssen, although not a stranger to an anti-Semitic rhetoric like a good number of the nationalists and conservatives in Germany (and not only Germany) started to criticize the Nazi's policies as too extreme and largely irrational, openly declaring his dissatisfaction after the anti-Semitic riots of 1938 known as 'Crystal Night'. Roughly at that time he also started to criticize excessive focus on the military production he considered dangerous to the economy of the state as such. In addition, shortly after opening the Institute of the Estates (Instituts für Ständewesen) that was substantially backed by Thyssen and focusing on presenting economy courses within the framework of the corporativist state, Thyssen started to be criticized by the party members that he favours conservative, Christian-socialist ideology that is not compliant with National Socialism. This eventually led to the closure of the Institute in 1936 and imprisonment of many students. Furthermore, Thyssen was often asking Hitler to reinstate or pardon politicians who, in Thyssen's opinion were competent but were deprived of their positions for what he considered to be unimportant reasons (like Düsseldorf councilman Carl Schmidt who was relieved of duty when it became known that his wife had Jewish ancestors) or to be replaced by yes-men. As a sign of protest, he also resigned from this seat in the Prussian State Council.

Immediately before the war broke out, Thyssen not only openly disavowed the Nazi regime, but also left Germany, understanding that his open critique of what was already a totalitarian state could be dangerous for him and his family. In his last correspondence to Herman Göring before the war, he stated that the large-scale war should be avoided at all costs, as antagonization of the major Western powers will cause Germany to become dependent of the Soviet supplies of raw materials, what will make it impossible for Germany to attain the rank of the World Power in the foreseeable future. In late September he wrote to Göring again, stating that there results of vote concerning war with Poland should be announced publicly (Thyssen voted against and was sure than many others did so). and that the prolonged war and restrictions of liberties will sooner or later plunge Germany into defeat, internal disarray or both. During the emigration, he disclosed the details of the support for the NSDAP yielded by German industrialists to a Hungarian reporter Revesz Imre (since 1940 naturalized in England as Emery Reves), close friend of Winston Churchill, what resulted in the publication of the book I paid Hitler in 1941.

Shortly after he emigrated, Thyssen was stripped of his German nationality and both his industrial assets as well as private property were promptly nationalized. Having initially left for Switzerland, Thyssen moved to France planning to completely flee Europe with Argentina being his first destinantion, but in 1940 he was apprehended in Belgium during the invasion of Low Countries by German authorities and subsequently arrested.

Thus, it can be seen that Friedrich Thyssen was not persecuted for being an industrialist, but rather he was considered an ally by the NSDAP until it became evident that he shares ideas not really that aligned with the Hitler's policies both domestic and foreign and is not afraid of vocally criticizing the latter nor that he seems to be able to blindly obey the Party's guidelines. Still, it was only after his emigration and open critique of the situation in Germany that he has been considered a political enemy, what led to his arrest and imprisonment until the end of war.