Increasing supply of the stock combined with the knowledge that the founder, who is an insider and large shareholder, is selling stock puts downward pressure on the price which makes the board look like they mishandled the situation.

My best guess would be:

He exits his position in a way that can hurt the investment optics of Uber.

> He exits his position in a way that can hurt the investment optics of Uber.

He didn't do that, though. He exited his position predictably and without huge newsworthy sales. As usual, Levine puts it better than I can; from https://www.bloomberg.com/opinion/articles/2019-12-17/the-se...:

> There is nothing particularly strange about this. At one point—basically before June 2017—Kalanick was the founder-CEO of Uber and owned an appropriate amount of stock for a founder-CEO, and now he is not the founder-CEO and is working his way down to an appropriate amount of stock for a non-founder-CEO.

…

> He has sold stock every day since the lockup expired. He has accounted for about 7.8% of Uber’s volume during that time

Great points, but it is highly unusual that someone in his situation would sell all of their stock so quickly. He probably couldn’t have sold it much faster.