My guess is that they had run the numbers on taking the company private before. Since the Saudis had approached Elon before and he denied their offer (for whatever reason) he probably was upset that they acquired a stake through secondary markets and tweeted their half-baked plan... (not a good course of action IMO)
Not super coincidental. It's incidental and on-purpose. What a day
How so? They've just got 5% of Tesla and he's talking about taking it private at +15%. It seems like instant profit to them just from the reaction to them buying it.