The calculus here is very, very complicated, and we shouldn't over-simplify it.
On 2nd and 11 at the 46, LV ran for 7 yards, setting up 3rd and 4 at the 39 with 0:38 left. That's on the outskirts of the kicker's range, but indoors, is doable. Let's consider the options.
A) If the Chargers let the clock run down, it's likely that LV lets the clock run down, takes a timeout at 0:03, and gets a FG attempt from 57 yards.
B) If the Chargers call timeout, then they force LV to run a play on 3rd and 4.
- If they stop them and call another timeout at, say, 0:30, then LV is faced with the difficult decision of either going for it on 4th and short at the 37 or attempting a ~55 yard field goal with time on the clock, or punting and basically guaranteeing both teams a playoff spot.
- If they don't stop them, then we get the outcome that happened
The Chargers were betting that by calling timeout, they gave themselves a chance to make a stop on 3rd down and that doing so would compel LV to punt because LV would not want to risk giving LAC the ball back in good field position with 30 seconds left.
Calling timeout there was the only chance they had to avoid giving LV a freebie FG attempt.
And, frankly, the 57 yard attempt would not have been much more difficult than the 48 yard attempt that they gave up.
I completely agree with calling the timeout because, as we now know, LV would not have simply run out the clock.