1) Aren't going to hire somebody for a leadership position because they met them networking --- they are going to hire them based on merit
2) The people in charge of smart companies aren't at networking events because networking events are a waste of time
Startups are a way to "level up" your career only because you can skip years of moving up a corporate ladder by starting at the top and building a successful company below you. This doesn't mean that by being a CTO of a 3 person company you are all of the sudden eligible to be a CTO at a big, successful company. The process of being CTO at your 3 person company and growing it into a big, successful company is what makes you eligible for that position at a different company.
The best insurance policy for your career is to be really good at your job, which means working on your job instead of networking.