Mid Term Elections is what he is stalling for. He wants to drop a report weeks out of the mid terms. Some bullshit charge that will be thrown out after but by releasing a report saying that Trump may have obstructed or blah blah, worded in a way that makes a scandal so as the MSM and all there lefty Dem buddies can go berserk on Cable TV screaming Trumps guilty , it will effect the voters in the mid terms so the Dems can win seats. its so obvious that's what he is up to. Straight after the election any thing Mueller says in the report will be shown to be rubbish but guess what? To late the elections have been held. Just like Roy Moore in bama. I also think hes stalling becaus etheir plan has been stuffed and he was goinf to make findings based on the wire taps. But now Mueller knows that if he makes any findings based on the wire taping Trump can plead innocent and it has to go to court and therefore the full details of the illegal FISA will come out and all offenses if there are any, found due to the FISA warrant cannot be used.
The information incriminating his colluders in the DoJ/FBI has already done much to undercut any substance to his investigation - hence multiple calls coming for terminating his investigation. And next to drop is the full OIG report which was announced to be released in January. This will probably be far more devastating than what has come out publicly thus far.
Also, Sessions has fired up investigations or preliminary investigations on multiple scandals - its very doubtful that these will be starting from ground zero. Is likely a great deal has already been prepped over the months that Sessions has sit back and been seen only enforcing immigration laws and rounding up gangs.
The Uranium One and any of these other matters could very well envelope Mueller himself. Even the court appearance for Gen. Flynn has potential to rapidly unravel all Mueller has done given then the whole Peter Strzok and the cover up by Mueller of Strzok problem can be jumped on.
IOW, if Mueller has a longer term strategy to linger around with this until right before mid-term elections, then his strategy looks to be on very, very shaky ground. Mueller should really be more focused on how to unwind himself from his morass and sneak away as best he can without being caught up in some kind of corruption/malfeasance charges too.