Actually, that's not true. The hitting line is exactly correct, but the "leading all Angels hitters" part isn't, because Trumbo has played in just six of the 11 Angels games and has only 19 plate appearances; most of their regulars have more than 40 PA.
Why is this? Because Trumbo is a first baseman/designated hitter, and the Angels already have a roster full of those. Thus, they tried him at third base during spring training; to be generous, he wasn't very good. He's started three games at third base since the regular season started and has been... well, bad. He's handled eight chances in the field and made three errors. Fielding percentage, as you know, isn't that great a measure of fielding competence, but when your fielding average is .625, that might indicate a problem.
So Trumbo's been benched for the last couple of games. Everyone's saying the right things, so far.
"As quick as I can progress at third, [it] will equal more playing time," Trumbo said. "It's all on me. That's the way I take it. That's why I'm putting so much work in."
Trumbo's replacement, Alberto Callaspo:
"Any time they give me a chance, I'm ready every day.… It's all good," Callaspo said.
Manager Mike Scioscia:
"He'll get in [the lineup].… We want to get him in there as much as possible," Scioscia said. "It's tough to say what his [at-bat] numbers will be; guys will get a chance to contribute."
The linked article above indicates that "some fans" think Trumbo should be given a chance to replace Vernon Wells in left field; Wells, though, has hit at least reasonably well so far (.262/.279/.500) and is currently leading the Angels in home runs with three, so you can see why Scioscia wouldn't want to bench him. Also, Trumbo doesn't have much outfield experience (32 minor league games and 12 major league games), so that might not help him or the team defensively, either, although clearly, left field is an easier defensive position than third base (and if modern outfield butchers like Alfonso Soriano and Pat Burrell can play there, surely Trumbo could).
But again, the Angels have a highly-paid player (whom they likely can't get rid of) already in left field. They also have highly paid players they do want at the positions Trumbo is best at.
What they really should have done is traded him in the offseason; there were teams that could use a hitter as good as Trumbo (though, to be fair, he didn't walk much and struck out a lot in his rookie season). Now, most teams are content to wait a few weeks or until they have an injury to go prowling for a trade.
In the meantime, perhaps rotating Trumbo through left field, third base, first base and DH, giving the three other regulars a day off a week, might be a reasonable solution. Because the Angels could really use Trumbo's bat in the lineup.