Again for the challenged readers, Notice in the original post where he says he replaced the main spring And the strain screw.
You evidently believe he adjusted the tension correctly?
Those most common reason is adjustment. It’s what shooters do to get a light trigger.
The next most common is the spring. Some shooters will install a light spring for the same reason.
The next most common is using other after market pieces.
The least likely possibility is damage, in my opinion.