LE has stated in search warrants and charging documents that they believe more than one person besides Wint was involved. That is a fact contained in those legal documents and not just Garrett's opinion.
Garrett gave an explanation of why those people weren't arrested. He said LE often finds it more helpful if they don't take them into custody and instead watch them closely. He also doubted the $40,000 was the only motive and mentioned a hired hit. I value the professional opinion of a 30-year FBI agent.
JMO
Take them in on lesser charges and they lawyer up and shut up. Also, might get bail. Compromises case to arrest, release, arrest again. More leverage to deal when make the most serious charges. Reasonable that investigators waiting for loot to surface, tests, working overtime with the bits and pieces, from receipts to bank bands to fibers and hair, to connect the dots.
I do value Garrett's opinion (any veteran FBI with a solid background in working homicides) and, although I don't think DW himself can reflect, even on his own simmering anger long enough to control his actions or to plan, he could have been engaged sub-contracted.
Following through on a hit theory, can we attempt a badly educated guess about WHY and WHO? I don't mean a name, or one of the actual cast members, but genus as in biz rival, angry neighbor, online crazy...oh, and why now?
No floating dumb theories or creating false buzz about the victims.
What class of person for what reason wants to torture and then kill ANY prominent CEO with any passionate avocation (could be golfing), a measure of wealth, a happy life, popular and well respected...We'd assume a secretary or gardener is collateral damage.
And the CEO's beloved college-aged son is home for the weekend and gets the brunt of the attack.
Amateur hit is tough because the range of motives can be tremendous. A total nut-cake can hold a delusional grudge against a 90 year ld woman she thinks her husband is plotting to leave her for OR a cold fish can rape pillage and plunder to lay hands on a deed to a rich farmer's land.
I do have to say, if this was not about money why wait for the 40k to put in motion the denouement. Was the 40 k just icing on the cake?