Here are a few things to consider:
Age and mileage of the vehicle: If your Volkswagen has a lot of miles on it, or is relatively old, it's more likely that other pulleys and the water pump will be starting to wear out as well. In this case, it may be worth it to replace them all at once to avoid having to do multiple repairs in the future.
Condition of the other pulleys and water pump: If the other pulleys and water pump appear to be in good condition, you may not need to replace them immediately. However, it's still a good idea to keep an eye on them and replace them as needed in the future.
Cost of replacing the pulleys and water pump: Replacing all of the pulleys and the water pump can be a relatively expensive repair. If you're on a tight budget, you may want to consider just replacing the idler pulley that sheared off and keeping an eye on the others for now.
Ultimately, the decision of whether or not to replace all of the pulleys and the water pump is up to you. If you're still undecided, it's a good idea to talk to a qualified mechanic who can inspect your Volkswagen and give you their recommendation.
