Is it better to create a new domain for a separate line of business or develop a subdomain?

Question

Search Engine Optimization

There is a main website of the company, which has several areas of activity. It has several subdomains - for different fields of activity. They are all more than one year old, there are links to them in industry directories, on some sites, and so on. Certain efforts have been made to promote them.
There is a fear that numerous links to these subdomains will "eat up" search positions or, in other words, interfere with the promotion of the main domain. Is it worth moving them to separate new domains or is it better to develop them as subdomains?
As I understand it, the big disadvantage of creating domains is that all promotion efforts will have to start all over again? Is it worth going for it?

Answer 1

Yes, you understand correctly that many results can be lost if transferred to separate domains (although not completely). Therefore, it is better to leave subdomains.

Answer 2

Mikhail
It is necessary to consider on a specific example:
1. If, for example, you are selling farm eco-products and want to open a branch, similar to the "tastier at home" service, this will not affect it in any way (although I would still create a new one)
2. If you are engaged in all those the same eco-products and at the same time selling auto parts is not logical to interfere with everything in one mess
. It's not very clear what you mean by "they will interfere"?
You need to engage in promotion (both paid and free), then there will be no problems.
PS, as I understand it, we are not talking about large-scale scaling of these projects? If so, then definitely a different domain