Single-threaded deals
One friendly contact is not a buying committee.
A single-threaded deal depends on one person’s time, memory and job. Your champion loves you, the price is agreed, and someone you have never met asks where the data is stored. Nobody lied. You spoke to one part of the group.
It is not only that your friend might leave. It is that the other seats are on the buyer’s shrug: "we did not hear enough, so no". Cover more seats early.
Find your way around
Learn it in the course, copy it from a playbook, see it work in a case study.