DrewSpark recently recorded a video detailing the behind the scenes of Sentinels' split. I made some notes for those who don't want to watch the whole video.

• the role swap at the beginning was for two reasons, first was getting dephh in the pack, the second being having more set roles especially the viper/KJ anchor role (he brought up how they were looking at LOUD with Less and NaVi with Suygetsu as inspiration and didnt want to do a DRX where everyone flexed the roles). Also interesting to note is that he showed a spreadsheet of his proposal of the role changes required and it had TenZ on Breach as one of the roles that was being tested at that point.
• the pancada to sentinels was a very early change, but they weren't sure who to put on smokes, they wanted a set primary duelist and considered having zekken or TenZ play smokes or even Senti and pancada back on smokes, leaving the other to full time entry. He stated that they thought that sacy was a slow, methodical player and dephh already had the synergy with zekken for the double initiators from XSET that really solidified their resolution strategy

Link: https://www.youtube.com/live/BXu8mVpLkYM?feature=share