Sending the cops in seems like throwing good money after bad. The ballots were already printed, etc.

The Spanish government regularly wastes Catalonian money, including sending in police to suppress this technically illegitimate vote. Whatever this vote cost to administer, it is a pittance in the grand scheme of things, especially considering the people seem to be willing to bear the economic burden of attempting to gain sovereignty.

If their crime is misappropriating funds for the referendum, then surely the police should be arresting the politicians, not harassing the public at large.

Because they were planning to spend millions of euro in an illegal thing, and use the results to try to legitimize the illegal thing in the eyes of the world.

Having 11.000 Spanish policemen in Catalonia, including the ones in the Lonely Tones ship, costs 33M EUR a day.