Lunging and pulling on lead can be due to over socialisation and owners encouraging their dogs to 'say hello' to other dogs whilst out on walks. Once dogs are in the habit of going over and stopping to interact with every dog they see. This becomes their default want and need. If a dog for whatever reason can't achieve this then frustration manifests generally in the form of pulling, lunging and barking at other dogs. Simply because they are desperate to go play with them.
How to prevent post ‘covid-19’ lockdown separation anxiety in dogs. Top tips to help prevent separation anxiety once we have returned to normality from lockdown.