Just wanted to to share this article from NYMag, as it is well-written, contains a plausible and comprehensive possible explanation:
(Including comments about the decision not to switch to IFR, the apparent 180 just before the crash, etc)
/intelligencer/2020/01/kobe-bryants-helicopter-likely-succumbed-to-common-danger.html
(I'm not allowed to post links yet, so add nymag . com to the beginning, minus the spaces).