I posted this before, but Rogers is looking to aggressively reduce their debt load after acquiring Shaw a few years ago. Rogers management has been vocal with investors (including on the last quarterly conference call) about monetizing their sports holdings (Blue Jays/MLSE) through either an IPO or partial/whole divesture.
After trying and failing to sign Ohtani and other marquee names during the last couple offseasons, they probably concluded the following:
Guerrero is the face of the franchise with mainstream fans and the most marketable player on the roster. Mainstream fans would be quite upset in the short-term if they traded him or let him walk.
Without Guerrero on the roster, they believed it would be more challenging to sign other marquee free agents to the roster.
$500M is a huge sum, but in the short-term, Guerrero's $40M per year won't hamstring the roster, given he's already close to $30M/year now.
Atkins/Shapiro probably concluded the contract was $100 - $150M too rich, but that Guerrero still had the upside of an elite player.
The premium above would be amortized over 14 years, the premium was worth it to Rogers as they look to maximize the current appeal and value of the team.
In the end, the short-term impact of losing Guerrero on the franchise's current fan and brand appeal outweighed the long-term possibility of an albatross contract, given the transaction Rogers is exploring.
I'm not defending the contract, I hated it and think we grossly overpaid. But as you hinted at, there were clearly other factors at play and I'm not going to browbeat Atkins/Shapiro for this one.