just talking to the wind here...but IMO, I still feel that MB's murder is related to her Austin Total Transformation trip and I believe CT was on the "target interest" list for good reason.
AT has been a trainer for quite some time & in looking at all his Instagram/Facebook/Twitter photos, etc he has trained lots of attractive women. But, he has always worked locally and close to home.
When he transitioned from IChooseFit to Camp Gladiator his lifestyle changed. Here's a link about his transition:
http://www.ichoosefit.org/feb-22nd-ichoosefit/
AT has 3 different FB accounts and one is his "Beastmode Garage" account where he posted about the fitness sessions he held in his own garage (in addition to bootcamps elsewhere.) And on 4/8/16 he posted on that account that he was having to work earlier days & later nights and didn't have enough time any more for his Jiu Jitsu or garage workouts.
And we know that MB was his mentor or was training him for Camp Gladiator. (at least I think that's correct.)
I'm not sure how far in advance the Austin Total Transformation trip was planned, but we know that MB and AT were there. So, AT had to travel away from home for this.
And *bam* - after AT returns home from Austin & is holding his first Monday morning Camp Gladiator camp - MB is murdered.
The timing of it just really stands out to me.
I think the motive for MB murder was extreme jealousy with the perception that AT was being pulled away from CT and his home by MB.
JMHO
I think this general set of emotions you are noting could be applied to many people in this situation. Someone gave a good summary several threads back, but they basically discussed how when one person in a relationship gets very involved with a new, time consuming hobby or career it can cause marital strife. When you add the hobby\career having the side effect on that person of changing the way they look physically as well as feel about themselves mentally, you add another layer. Now add that the career often has you working around others that share this passion for the career....it can be hard to work through and you can easily see how it would cause some jealousy. Obviously, plenty of marriages handle it fine, but it isn't a stretch to see it could cause problems. I personally think this jealousy is what got MB killed. Now, I could apply that to several people in this whole scenario, so thinking it was an act of jealousy doesn't clarify who I think SP is. It still puts many names in the mix, both male and female.