The "government" didn't do much at all, there was no real oversight or guarantee like there is today. The whole concept was novel at the time so there was no law and there were no real procedures. The Dutch Republic may not have had an official king, it also sure wasn't a democracy with real, independent institutions or anything like that. The country was led by a democracy-lite system of nobility/rich people that feels a lot like how early American voting worked (but divided even less evenly).

The closest thing to an involved government wasn't really in favour of trading in immaterial goods at all. Something close to government intervention did happen in one of the two involved government systems after the bubble popped, but it was effectively unratified and useless (the local equivalent of a supreme court even ruled that the government couldn't interfere with the tulip trade).

The entire thing was just a club of a few hundred relatively rich people throwing themselves at a bubble. Most people didn't have the means or money to participate.

The "mania" name is an insult to those who partook as much as it described the trade bubble. It's not related to the modern psychological definition of "mania" that came much later.