For most people, the mental image of SEO is direct advertising.
Either people think that SEO is free Google ads. Or that most people would convert on a single visit to a website.
Typical thinking - You rank on page 1, they click, read your blog or landing page and then buy.
In reality SEO works like this - You rank on page 1, they read your material, and you stay in their mind. Most likely they would buy on few more touches, like seeing your brand in some other channel and a lot of times even reading your other blogs that came on top of their internet search.
The core of the aim of SEO is to be one of the touchpoints for a prospect to sway towards you. Ofcourse, many a times they will covert direct as well especially if your content is more bottom of the funnel.
Content Marketing should be seen both a brand building channel to a higher extent. And as a sales channel to lesser extent. Results build over time.
Also, we should consider SEO as a forever investment and thing. It's an ongoing process where you turn your website into a Wikiperdia for the kind of audience you want.