Let's get this out of the way real quick: We don't really know what accounts for a player's power level. Most likely this is a combination of rank power levels (as described in https://splatoonwiki.org/wiki/Splatfest_Power) with an Elo-based score evolution (as seen in splatfest and leagues) plus another factor that I'll detail later which is more linked to the team-based nature of Splatoon.
The problem here has several faces to it. We need to explain the following elements we can observe daily:
- How one skips ranks even with cracks when one doesn't with no losses?
- How the gauge increases differently for apparently random reasons?
- How one gets cracks instantly and sometimes only after 3 games?
The starting point of my reasoning comes from what we could all see when splatoon was released or, more recently, when clam blitz came out.