The report is actually pretty sad. Brosnan was definitely in the wrong here and deserves his punishment but the NCAA does look pretty harsh as well. Timeline is basically:
1. Brosnan becomes friends (as in, has them over for dinner often) with the parents of "Prospect 1" and "Prospect 2" during his time as a HS coach
2. Once Brosnan takes the UCLA job he continues being friends with the parents. Per the NCAA report, this is already a tampering violation, since the bylaws do not differentiate between athletics related and non-athletics-related contact with "individuals associated with an athlete"
3. Prospect 1's mother gets cancer, Prospect 2's dad has a series of strokes; Brosnan continues has conversations with both sets of parents (still a violation)
4. On a few occasions, both sets of parents mention the possibility of transferring; Brosnan tells them he can't talk about it until P1/2 are in the portal (he's wrong, he can't even talk to the parents at all about anything)
5. Transfers happen, coaches get mad, NCAA investigates
6. Brosnan delays meeting with NCAA, claims he wants to review the data they scraped from his phone (I guess the NCAA just hoovers up all of your personal data when you piss them off?) and this is deemed a non-cooperation (I don't really follow this part too well, it's not clear if he was acting on advice from his attorneys or what; the report claims it wasn't related to the phone data)
Items 2-5 are the reason for the tampering violation, item 6 is the reason for non-cooperation.
Again, he was 100% in the wrong in terms of what the rules are but it's pretty brutal to tell a friend "hey because I have this job and because your kid runs in the NCAA, I can't pick up the phone when you call me about your wife having cancer."