That may actually be the next project of these physical casinos, create their own online sites and setting up/managing it would not be hard on their end. So yes, online gambling will boom in no time. They can get their players easily as they already have their own patrons so they will just send a message to these loyal patrons that they have online site and they are on the way.
However, this is a rather laborious process. Just as when moving from one place to another, we risk losing some things, so when moving customers offline to online there is a risk that they will be lost. When a large casino announces the creation of an online cell, a lot of scam clones appear that will disorient and lure some customers to themselves. And given that the level of preparation for working with web applications is different for everyone, the percentage of trapped clients can be quite high.
I don't think most people will be trapped into clone sites if the casinos create their official online site and invite everyone from their physical casino itself but it is not going to happen in near future so there people might already moved to fiat or crypto online gambling sites to tackle lockdown boredom.