I think Coach is playing a good game right now. He's manipulating those he can manipulate in creating an alliance to go into the merge. While it isn't always the case, usually the team with the numbers at the merge picks off the other team - we lovingly call it being "Pagonged" after it happened to the Pagong tribe of Season 1. Of course, occasionally the smaller team makes a run (as happened with Russell's team) or someone switches...but as a rule, numbers and loyalty offer the best chances going into the merge.
Coach has been handling Brandon masterfully - he realizes he's a loose canon but is managing to keep him under his wing. He's created a strong bond with Sophie and Albert, so much so that Albert gave him the clue the led him to the HII. And Coach has turned Edna's desperation into a bond, as well. So love him or hate him, as they say: You can't argue with success.
So Mikayla, who was obviously strong and could have performed better, failed in that she didn't listen to the advice being given her. It wasn't just Coach telling her to not do it one-handed, and maybe if she'd tried she might have been more successful. While Coach didn't knock out any targets either, at least he was trying his best. If he had been doing it one-handed, would he have changed coarse and tried something different, especially something everyone else was doing? I think he would have, but we'll never know.
In the end, I think he made the right decision for himself - and after all, they're all playing for themselves in the long run. A team doesn't win the game. And while some of them will comprise the jury that might vote for or against him if he makes it to the end, so far he's not got any real enemies, except for Christine, who is a long shot for returning to the game.
That's my two cents