Then it doesn't fix the bubble because you're still giving regular people very low interest loans which they use to bid housing prices up to the sky.

Whereas if you raise interest rates, housing prices go down relative to wages without any change to property taxes.

You cannot discourage ownership of “investment property” without also discouraging landlordship — which raises rents.

You can tax unoccupancy, which is what Vancouver does. Having a tenant in the house actually makes it more difficult to sell and has overhead (risk in damage and non-payment, often both), so taxing empty houses puts some pressure on speculators to rent the places out at least.