Sure, but then you should have to have a conviction on those other crimes. It’s strange to consider stuff that wasn’t proven. If the crime was committed and the state is sure, they should charge him and then use the first conviction in the sentencing for the second, if they want to.
That’s not what happens in practice. The other actions of those charged are absolutely brought in as evidence whether they were actual crimes or testimony from others that knew those charged. This happens all of the time.