This was a smash and grab of a church with some thought used for finding a quiet spot for the smashing part and to make a faster escape with bicycles.
It was admittedly clever to have a boat ready, since it's easy to vanish to Mälaren, make a landfall, dump the boat and switch to a getaway car.
Svenska kyrkan really needs to do a risk assessment and take this seriously, since it is not the first time and won't be the last either and relying on the good will of people is not a strategy for preventing theft of historical artefacts.
Why would they be "complete morons"? They successfully completed a quite difficult heist.
Even if they don't have a buyer lined up, this takes a lot of skill and smarts.