There are 3 parts to this, the Dossier (who funded it), What did they use the Dossier for (the unconstitutional unmasking of US citizens) the Russian Uranium (corruption Story).  When looking for the truth you always start at the most vulnerable or weakest point which is the Dossier itself.  Just with every other scandal which has involved a POTUS it is rarely the crime that gets people caught, it is usually the cover-up.  That is why the Dossier is important, it was the only real piece of evidence which might have implicated Trump (which is why it was important to keep Mueller on track and pointed the right direction) and now appears that it may bury its funding source and it has the potential to open the other 2 items up and suck it Mueller, Comey, Lynch, Clinton (both of them), Rosenstien, and a number of Obama surrogates; and, like it or not Obama.  Obama is a narcissist, his weakness/downfall will be his arrogance.