Dale (along with Rogers) opposed Jared Cohen and Sarah Robertson on their plan to repackage the MBS products, or maybe it was the specific method of repackaging, either way... After his exit interview and packing up his desk, he's talking to Emerson - he asks "who was it?... Robertson?" which clearly points to the internal politics.

Sam was constantly having "I told you so" moments with other executives, including the one who fired Eric, implying that they all had a good understanding of what they had been doing all along but willingly chose to ignore the risk. Laying off the risk team was the next natural progression of this, because they were no longer a real part of operations at the firm.