How could a man facing trial for helping kill his wife and sexually assaulting dozens of women, while pledging support to the Islamic State and obsessively challenging his conviction for sending hateful letter to dead Diggers' families, be free to get a gun and walk into a city cafe?

Clearly, a high-powered inquiry headed by top officials, reporting within six weeks, is an appropriate response from the federal and NSW governments.

But not all the answers will be neat and tidy.

Yes, the failings of the NSW bail system seem fairly clear. There are also significant questions about co-ordination and co-operation between state and federal authorities. Monis was one-in-a-million for the peculiarly broad spectrum of his crimes and transgressions, who wouldn't fit well into the enmeshed machinery of national security and law enforcement.

Was he an Islamic extremist or a plain criminal? State authorities largely deal with the criminal aspects and federal authorities the extremist ones. Was his atrocity early on Tuesday morning an act of madness or terrorism? Unfortunately the human mind can't be so easily disentangled and therefore whether this unique individual was primarily a state or federal responsibility is very blurry.

His online Islamic extremist rantings, while vile, probably didn't merit full surveillance by federal agency ASIO – not on their own, anyway.

But didn't the murder and sex crime charges have a multiplier effect on those considerations? Perhaps not to a seasoned national security official. A man accused of accessory to murder or sex crimes against clients while working as a "faith healer" isn't necessarily more likely to carry out an act of terrorism.

Yet he was apparently monitored by ASIO after sending the letters to fallen soldiers' families, which raises the question: if he was seen as enough of a threat to monitor then, why not later, even after he was charged with serious crimes?

Likely it was a matter of resources and priorities. Surveilling people is expensive, resource-hungry work. Round-the-clock surveillance takes three shifts of between 10 and 20 officers – it is reserved for the most serious cases.

It also takes warrants, which expire fairly quickly and need to be renewed. Or it takes control orders – which were such a dramatic measure when they were introduced by John Howard that they have only been used twice in Australia and were recommended for abolition by the former national security legislation monitor.

Will governments be prepared to further tighten terrorism laws? Federal laws have been toughened three times this year already. Will they be prepared to spend more money in times of fiscal hardship?

When people ask: why wasn't Monis being watched? The answers the inquiry will have to find won't be simple ones.