Introduce environment variable VAGRANT_DEFAULT_PROVIDER

export VAGRANT_DEFAULT_PROVIDER=vmware_fusion

Vagrant.configure("2") do |config|
  # ... other config up here

  config.vm.provider "vmware_fusion"
end

vagrant up --provider hyperv

vagrant up --provider docker

vagrant up --provider vmware_fusion

vagrant up --provider vmware_workstation

vagrant up --provider virtualbox

VirtualBox is the default provider for a vanilla Vagrant setup.