The problem is the bus tourists, arriving in droves, walking quickly through the crammed city center, maybe buying some junk made in China, and leaving shortly afterwards. This is an annoyance for guests who stay longer, and for the businesses not seeing any significant revenue from bus tourists.
Therefore the number of busses per day had been limited, the entry ticket has been raised, a time slot system has been introduced, and the minimum stay for bus tourists has been extended to 2½ hours.
At the current situation all this is moot, of course. But Hallstatt would like to see tourists staying for a night at least, taking their time to enjoy the beauty of this town.