The problem of the big parties as CDU and SPD, along with their tails FDP and Greens, is that many people - especially in the east - feel ignored and neglected. For example in Saxonia the CDU government created industrial centers which do grow and produce jobs, but
a) these jobs are heavily subsidized by the state (up to 50k Euros per job per anno)
and
b) other regions are neglected completely.
Up to 80% of the young people do emigrate into the western federal states because they don't have a perspective in the east. There is no economic growth in large areas with average unemployment rates of 20-25%.
This is one thing. The second one is the basic ignorance of the "democratic parties". In the former GDR voting went this way - the SED and its cronies put up a list of candidates and the voter could vote either yes or no. Today with all larger parties propagating the very same policies there is no real difference to said ex-GDR votes, with the exception there is no "NO" on the ballot. More than 40% of the people did not vote at all and those who did considered voting for the rightwing extremists a valid sign of their protest (according to a statistic 80% of the NPD voters did vote for them out of frustration and protest).