Uber Technologies Inc.’s new board member, David Trujillo, spearheaded TPG’s investments in four startups now valued at more than $5 billion each. After a misstep by his boss, he’s taking a seat at one of the biggest -- and most precarious -- of them, whose fate increasingly lies in the hands of its investors. Trujillo, 41, joined the board of Uber this week, replacing TPG Chairman David Bonderman, who resigned after making a sexist joke.