Question about fiction writing: how do you make the reader care about the first event?

I'm trying to reconcile two pieces of writing advice:

1. Start right before the first significant event. Starting too early (e.g., when the main character wakes up on the day of the event) is cited as a common beginner mistake.

2. The reader needs to be invested in the characters before plot points land effectively. E.g., if we portray a deep betrayal, but the reader is not familiar with those involved, they won't care.

The apparent contradiction I see is that we want to start with a significant event, but we also need to build rapport with the characters first for it to matter to the reader.