I want to say a few years ago there was a "positive" verdict in a jurisdiction in Texas which set precedent which is why you see filings over there.

Let me see if I can find a reference and I'll update this comment.

EDIT https://www.eff.org/deeplinks/2017/05/supreme-court-ends-tex...

Initially, they developed a specialty in that type of case. You can't expect to walk into an average court that's unfamiliar with patent law and leave happy.

Over time, they were bribed with public amenities by large companies. You know, the usual.

Now some litigants are moving elsewhere to avoid the above.

Yes. The main attorney specialised in patent law there is the son and nephew of the judges.

They made a business of it

Back in the early 1990s, Texas Instruments was looking for a district to bring its patent litigation. The federal district courts in Dallas and Austin were clogged with criminal cases. East Texas was relatively open for civil suits to proceed quickly: https://www.texasmonthly.com/politics/patently-unfair/

The district is also not as random as people make it out to be. It’s a few hours east of Dallas, and includes some of the rich suburb/satellite cities like Plano. It’s got a significant oil and chemical industry.

Conservative area where a lot of companies spend money to be known to be the 'good guys'.