No, they were certainly not. According to the population census of 1925, around 564 000 Jewish Germans lived in the Reich. That's around 0,9% of the total population. In the first half of the 20th century the Jewish community of Germany was not a growing, but a stagnating, even slightly shrinking one. -- Totally contrary to the contemporary perception of a strong Jewish influx. This was probably created by the more recent immigration of 108 000 Eastern European Jews (so called Ostjuden in German), who on the average were poorer and more openly religious, even orthodox than the indigenous Jews of Germany. On the whole, the Ostjuden were a more "visible minority" than their German fellow believers.

The Jewish population was concentrated in the largest cities of the Reich, around a third in Berlin alone. Their occupational pattern was relatively stable and -- as in many places -- the product of historic pre-modern practices of exclusion from certain professions. In relation to the total population, the Jews were overrepresented in the areas of small business like retail (often self-employed), in trade, and (more well-known) in banking. They were underrepresented in agriculture and in the industry. The three large department store chains of Germany were found and owned by Jewish businessmen.

To sum it up: the German Jews were a highly urbanized, bourgeois, middle-class community and highly integrated in German society.

In addition to LBo87's answer, I'd like to add on the following: power and wealth are not necessarily connected. This is commonly played out in societies across the world: groups, like the Jews in Europe who became wealthy as a result of artificial constructs that either blocked them from getting out of or entry into particular industries where particularly vulnerable.

The reason for this is as follows: there are really four major ways for money to influence politics: direct insertion of money into political affairs, the formation of ideology through funding certain projects, the role of investor into certain projects, and the use of violent repression (although this only works if the person in power and the wealthy are one and the same).

The problem with the past is that of these four, the direct method of bribery or lobbying was applicable to an extent (I can't directly comment on this, but LBo87 gives some color on exactly how limited an influence the Jewish community would have been); the formation of ideology was almost non-existent because of existing barriers to entry for any Jewish person into certain industries as a result of discrimination (both legally and socially); and the role of investor basically was muted because other people, at the time, had capital as well with competing interests. So ultimately, their power was extremely limited in terms of actual political and social influence.