Corbusier's ideas were often part of the inspiration, only to get heavily pared down due to cost cutting.
For example, a lot of standardized blocks in USSR were originally planned to be made from large "library of designs" to provide varied and well adapted neighbourhoods, however after first few went through the cost cutting measures meant that they were replicated en masse.
Another example is one I have lived in - the longest building in Poland, at over 1.5km length, nicknamed Beijing by many due to super-high density. Critical changes into how the building was built were made by building company on occasion when architects were not around, resulting in long-term damage to comfort and quality of living. Once the architects were back in, it was too late to fix as you'd have to rip out the foundations and start anew.
Several other more "Avant garde" neighbourhoods in Poland suffered from similar issues, often caused by policy that was supposed to encourage innovation, where "rationalisation proposals" (not a good translation but close) that, for example, would lower the cost, were rewarded and often not well checked (if at all). The initial cost savings then turned into heavy issue later on.
A lot could be also said with regards to non-design problems during building, which caused issues due to materiel deteriorating sitting outside waiting for shipment of components necessary to build the required predecessors to the use of the now-rotting ones.