Why didn't Hoster confiscate Frey lands after Robert's Rebellion?

Frey's seems to pretty much control northern Riverlands as most of the houses there seem to be sworn to them, and they seem to control the only trade crossing in northern Riverlands. Not joining the battle until the results were determined seems like a perfect opportunity to dilute Frey power by confiscating lands and raise new lords at east of the Twins, or at northwest of the Twins. Plus, Tully's have marriage alliance with both the Starks and Arryn's who could help enforce these changes in power structure of the northern Riverlands. So I want to ask the community why Hoster did not use this opportunity.

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u/RockHunterHelmsley — 4 days ago