ThePointsGuy is a blog aimed at sharing credit card travel points tips, and all of the offers they share use a referral link so that TPG gets paid for everyone who signs up for a credit card. The entire website is one big advertisement (albeit one with useful advertisements if you're in to churning)
It's inherent in the functionality of The Points Guy's business model. Write pieces to bolster the various vendor's image. On the positive side, TPG isn't tied to any one particular vendor and does a good job of highlighting the merits of a variety of vendors.
It doesn't say it isn't sponsored or otherwise a promotion. I mean, there is a grey area, and it seems plausible someone would deliberately be in that area.
It only says Delta advertises on the site.
It DOES NOT say this is sponsored content or otherwise a promotion of some sort by Delta.