2. The potential fit with Keenan Allen on the LA Chargers
This one is just too obvious. Allen and Adams would be a perfect fit in terms of play style. Both have said as much publicly:
Besides all of the reasons it would be good for the Chargers, I'd get a kick out of watching Allen and Adams run routes next to each other on the All-22. It would be an NFL Game Pass session filled with absolute bliss every week.
Both receivers wouldn't have to worry about double coverage if they played together. Opposing defensive coordinators would be forced to make incredibly tough decisions. In addition to the defense being troubled by just the idea of them being together, the Chargers could still have some combo of Jalen Guyton, Tyron Johnson, and Josh Palmer depending on how things play out.
The counterargument to this is probably that Herbert makes his receivers better. While that's true since we saw it on display in 2020, I'd argue that Adams makes the quarterback better too. It's not a coincidence that Rodgers had the best season of his career while Adams was named an All-Pro for the first time. Yes, Herbert could probably shoulder more of the burden himself, but that's not a good reason that he should.
Philip Rivers had some years with pretty questionable receiver talent during the 2010s. The Chargers can afford for that to not be the case now.