How to get hard-to-reach people over the long run

I've been reading through almost all 400+ IndieHackers interviews and almost nobody talked about HOW to actually reach decision makers at medium and/or bigger companies, except this guy:

We used the old bottom-up model, as we sold initially to individual loan officers. Then after a couple of years, we were finally able to "grow up" and speak to the decision-makers at mortgage companies and banks. So the single loan officers who became our customers then introduced us to the decision-makers — the good old land-and-expand.

source: Floify, SaaS for mortgage lenders.

A pretty interesting approach...start with the easy-to-reach people, and then once you gain their trust, ask them to introduce you to their "harder-to-reach" peers.

Have you guys had recent success reaching key decision makers within a company consistently?