It's true that if the similar companies in question got dissolved, the trademark owners are not likely to oppose your application. However, this requires thorough research because even companies that don't seem active online may simply use different distribution channels. They can also be in the process of being set up. In many jurisdictions, a trademark doesn't have to be actively used for the owner to oppose your application (unless it hasn't been used for several years, at which point you would be able to challenge the opposition).
You can probably already see that the answer isn't straightforward. The final answer would depend on your brand, the identified similar brands, the nature of the similarity, the country of registration, and finally, why you consider them to be non-existent. Since there are a lot of variables at play, we would recommend consulting an IP professional.