How were fares and yields from LGB? If they can get better fares from LAX, especially on transcon flights, then it's probably a win for JetBlue in the medium to long term. No longer having to worry about the curfew is a bonus, although it's not like they were violating the curfew just for the fun of it, and the low slot utilization suggests low yields, as it was better for them to prevent someone else from adding a flight rather than adding one themselves.
What will be more telling is if Southwest adds flights (if they see that there is money in LGB) or if they pull back (if they were just competing with JetBlue).
Oh for sure LAX will give better yields. LGB was hemorrhaging money. So you are right in that JetBlue is the winner here, for now.
The thing is, IMO of course, if passengers have to go to LAX, there's no guarantee they will fly JetBlue, especially if another carrier is cheaper or has a better schedule. Outside of COVID times, AA and DL also had a small complimentary meal in Y (on JFK and I imagine some other transcons) which is a step up from B6 no matter how you spin it (OTOH, B6 has the free WiFi, though with T-Mobile you get at least some functionality with Gogo). Basically, if I have to go to LAX, I really have no reason to take JetBlue unless I'm in Mint, I'm connecting, or I'm Mosaic. If you have Priority Pass, you have Even More reason to take AS or DL. When push comes to shove, ceteris paribus, I just don't see that many people being willing to pay extra or sacrifice a better schedule just for The JetBlue Experience
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-J.