It's a bit over-sensationalized in the article.

The part of Israel's history that gets tagged with ???s mostly concerns the period before the burning of the first temple in 586. From 586 onward, Israel's history is fairly well attested and can be cross-referenced.

What's generally questioned is the depiction of the kingdoms of David and Solomon as very powerful and influential states, mostly because you'd think if they were the Assyrians, Babylonians, Egyptians, and Hittites would have mentioned them and the archeological record doesn't support such a state existing. There is at best 2 or 3 references to Judah in their records despite them talking about this region a lot. It was a really important region for the big empires of the age.

But there's been growing evidence for years, sporadic as it is, for an proto-state Judah. The Tel Dan Stele sure seems to reference a 'House of David.'* It's generally speaking, taken for granted that Judah existed before 586, existed for a good while, and was possibly/probably a regional power. What's questioned is if it was really as strong a kingdom as the Bible suggests it is cause we'd expect to see evidence for such a state where we're not finding it.

Put another way, it's not really a question of whether the Kings of Judah existed or not. It's mostly a question of if the Bible is an accurate record of their history. There's no real reason to doubt these men existed. We accept king's lists at face value all the time. There's contradictory evidence though as to how powerful and important these kings were regionally and in the broader political network of the Near East of the ancient world before 586.

As the OP article suggests, this discovery is mostly about chronology, which is a very fucky and hard to detail subject because until people started recording dates it can be really hard to gauge when things happened in relation to other things. We have to fallback heavily on things like wood rings, geological events, and cross references to try and nail down the timeline of human history before the 6-5th century BCE.

This find is cool because it purportedly has a date (said because this will be investigated and confirmed) which is a pretty big find. Biblical Scholars have argued for a long time that parts of the Bible come from now lost royal records, and old stone carvings are useful for supporting that especially if their old. I do note however that the OP article fails to explain how these inscriptions were dated.

Their having a date isn't the same thing as being written on that date (the oldest date given in the Maya world is hundreds of years before the inscription itself was chiseled). They kind of skip over that in this article and simply claim the age of the inscriptions.

*(there are people who question the translation but they're more and more a minority and alternative translations have not been convincing)