The narrative (whether correct or incorrect) is that Bitmain tried to block an extension because it would disable a feature in their hardware that was saving them tens to hundreds of millions of dollars per year on electricity.
That has nothing to do with patents, it's (supposedly) an advantage they had over the competition, of course they are going to defend that advantage.
Patents for mining hardware though are unenforceable overall. The problem is that lots of private mining farms exist, and nothing is stopping one from developing a chip that is in violation of many patents, but then never releasing the hardware publicly. There would be no way to tell that the patent is being violated, especially because mining is more or less anonymous in the first place.
That has nothing to do with patents, it's (supposedly) an advantage they had over the competition, of course they are going to defend that advantage.
Patents for mining hardware though are unenforceable overall. The problem is that lots of private mining farms exist, and nothing is stopping one from developing a chip that is in violation of many patents, but then never releasing the hardware publicly. There would be no way to tell that the patent is being violated, especially because mining is more or less anonymous in the first place.