why was this painting stolen 3 times ?

Thieves have stolen the painting Two Laughing Boys by Dutch golden age artist Frans Hals from a museum in the Netherlands, police said, the third time it has been taken.
The artwork, valued at $18m by one expert and dating from 1626, was taken from the Hofje van Aerden Museum near the city of Utrecht before dawn on Thursday, with thieves breaking into the building from the back door