The timing of the sales was predetermined under what is known as a 10b5-1 plan[1], named after an SEC regulation that allows company insiders to avoid insider trading charges by setting up a schedule of sales in advance (typically a year).
I only know because I drove a CEO for the company I worked for to a meeting and we got to talking about stocks. He explained this loophole to me as his way to effectively trade how he wants with legal protection from insider trading.
From Wikipedia: "After Rule 10b5-1 was enacted, the SEC staff publicly took the position that canceling a planned trade made under the safe harbor does not constitute insider trading, even if the person was aware of the inside information when canceling the trade. The SEC stated that, despite the fact that 10b5-1(c) requires trades to be irrevocable, there can be no liability for insider trading under Rule 10b-5 without an actual securities transaction, based on the U.S. Supreme Court's holding in Blue Chip Stamps v. Manor Drug Stores, 421 U.S. 723 (1975)." [0]
The idea being the thing to maybe pay attention to are buys, not sells from those folks.
I worked at a place once where at a meeting the CEO was asked about selling a bunch of stock. He was pretty honest and said something like:
"I love this company and I'd love to 'double down' on it but as a private person most of my assets are in this company and it's time to diversify, even if just for my kids."
Anyway that was received well by most folks there.
The CFO noted "Not me I'm all in!".
Epilogue, the CEO was smart, the CFO less so... (granted CFO still did alright)