Campaign Threat Mechanic

So in the campaign, planets have a threat meter that increases by an unknown amount for each connected hostile planet. Sometimes putting a fleet on the threatened planet will reduce the threat, sometimes it’s not strong enough according to the turn summary.

The only for sure way I know to eliminate threat is to capture all connected planets which makes hub planets with 3+ connections quite a challenge. Is there any info on what triggers big threat gain? Any strategies to reducing it other than placing a massive fleet on it? Also, does the game randomly wait X turns after 100% threat to throw an enemy fleet at it? I’m curious as to how this threat mechanic works to deal with it better.

As far as I understand it, if your planet is linked to a different planet, and the value of the fleet there is lower than the value of the fleet on a linked planet, the threat increases by an mount depending on the difference. Threat decreases on its own if the fleets are matched.
I don’t think the number of linked planets affects it, strangely enough.

After beating a campaign, there’s really no on the map indicators, you just adjust based on the turn summary and have a fleet ready for attacks on your front line planets.