Speculations:
Prince Ahmad bin Abdulaziz returns to Riyadh with UK and US security guarantees and a brief to cut the crown prince down to size
https://www.middleeasteye.net/news/exclusive-saudi-dissident-prince-flies-home-tackle-mbs-succession-58983364
Ahmad was never very good at taking on the role of the big guy at the top. I recall his post-Hajj briefing in 2012 when he essentially spent half of it thanking MbN amongst plenty of inshallahs. He didn't come across as a man of strength, or authority.
Assist other senior princes with taking on more responsibility and evening out power balances within the family. This is my hunch, I have no proof of it, but I know this. MbS is totally safe, and this development at most is about capacity in the Royal Household, not some plot.
https://twitter.com/MStephensGulf/status/1057594067595522048
Expect a busy weekend in the palace.