bleepbloop

I feel like this is unique, and I'm not quite sure how to gauge the situation. A professor that I worked with recently left for a TT job at a different program. We had worked closely and this professor was very supportive, ultimately they were the one who convinced me to pursue grad study. They are writing one of my LORs. The program in which they currently work is my top choice, and I identify this person as a POI and explain our past work in the SOP. Coincidentally, they will be on the admissions committee. The stars have all aligned, so it seems. However, this is my first application cycle and I'm not very familiar with how things work. I also don't want to be presumptious, so I was hoping for some honest feedback. How much weight can something like this carry in a decision?