> Like, why?

The answer, as succinctly as possible: cognitive dissonance.

This is exhibited in every human endeavor, but it's particularly acute, or at least more apparent to simple analysis, in business. In business, anything that diminishes the perception of value is a threat to earnings. Business people don't tolerate the existence of such perceptions in their minds. They readily adopt whatever mental state is necessary to deny realities that reveal a lack of value in whatever work product they sell.

In this case, someone demonstrated a weakness in a lock design. In the minds of the business people behind the product, this is impossible. Their locks are awesome. Best locks in the world! Therefore, the only conceivable possibility permitted, in their minds, is fraud or some other actionable offense that can be feasibly pursued in court.

The role of lawyers in this is a symptom, not a cause. Lawyers are paid to exhibit the necessary cognitive dissonance their clients require. Whatever aberrations or iniquities arise from this are simply denied by yet more cognitive dissonance.

Even if they know they would lose in court, lawsuits are expensive enough that threatening to sue or filing a lawsuit is often enough to get people without deep pockets to do whatever you want.

I don't know if that was the reasoning in this case though, considering that they didn't drop the lawsuit once it was clear that the youtuber wasn't going to give in to their demands.