Sorry, was busy the last couple of days. Additionally, since I frankly have my own cases concerning similar fact patterns and because I no longer own Watson in any dynasty leagues, I haven't been focusing on the Watson saga all that much so had to review.
The issue being discussed here - whether prior bad acts can be admitted to prove a later in time allegation - is a complicated one with no easy answer. Frankly, both of your thought processes are not terribly off-base. Further, since this appears to be a Texas case and I'm not licensed in Texas, I am not going to try to interpret Texas law. This is important to note because Texas may have a particular law or a particular court case setting a legal precedent that I'm not aware of.
In short, prior bad act evidence are generally inadmissible because prior bad acts likely are not relevant enough to outweigh the inherent prejudice they would have against a defendant in a trial. Also, courts tend to want to dissuade their admissions because it could create a trial within a trial (where a defendant would naturally have the desire and quite possibly the right) to defend himself against the prior alleged bad act and the trial goes longer than anticipated, juries may get confused, etc. Accordingly, usually courts will not admit prior bad act evidence because there is a loose correllation at best between the commission of a previous one and the state should not be alleviated of its burden to prove a subsequent offense beyond a reasonable doubt.
However, at least in my jurisdiction, prior bad acts may be admissible for other purposes, such as proof of motive, opportunity, intent, preparation, plan, knowledge, identity, or absence of mistake or accident. Additionally, in my jurisdiction, there is a carve out exception for alleged sex offenses (whether criminal or civil) whereby prior bad acts could prove a character trait. Those bad acts must still be evaluated by a judge through a multi-factor analysis and, ultimately, the evidence must still be probative (meaningful) enough that it is not substantially outweighted by the prejudice to the defendant.
Here, assuming the eyewitness accounts are so similar that Watson has a particular modus operandi (MO) for how he commits the crimes, I could see a very good argument for its admission and would think a judge would provide a jury instruction explaining to the jury that the evidence shows a pattern but the jury must still find that the state met its burden of proof for all of the elements of the alleged crime they are deciding about. That said, the defense will almost certainly raise the issue before trial and the matter will be argued about and decided by a judge beforehand.
to the poor every day. But just because you mean what you say & say what you mean doesn’t insulate you from someone who isn’t as wholesome and pure. 
