Found a real niche niche. Any advice?

We always hear the same advice: find a niche to open a biz in it so u have less competition etc then we go thru life and we really don't see this niches because everything feels oversaturated.

I have worked with over 200 companies in all sectors, I learn about their biz in order to do proper marketing for them but never felt that I found a real "there's hardly anyone working on this niche" do you know what I mean?

4 months ago I saw a job post asking for a marketing manager, I applied, research the company. Never heard of this type of biz before, research competition just 2 more. even in their website there is an article from 2007 saying how niche their business is and it was making 4.5 mill back then. it had 25 employees in 2007 and still has 25 in 2026. their whole marketing is literally stuck in time. Still the owner he does everything and decided after almost 3 months interviewing me not to hire anyone "we talked every 2 weeks and he always forgot what we talked previously" every other staff approved me for the job.

Anyway, I still intrigued. because not only they lack competition in USA, is mostly global. This company Won't grow. the owner wants to do everything himself and dont want to change anything. I talked with staff and based on our meetings he is all the time flying around in sales meetings etc but nothing can get approved if he doesn't edit it himself. They sell a very unique type of products they manufacture in USA. their competitor makes a similar one but more expensive and harder to use.

What would you do in this case? knowing that in a few years they reached 4.5 mill and 19 years later have hardly any competition and they are doing nothing to grow. and theres a need for their product globally.