What else could he do?
He knows how good Cousins is. He's seen him him practice.
He knew in that playoff game last year - he goes out after collapsing a 14 point lead, Cousins comes in and wins, people talk.
He knew he wasn't ready to come back yet - he didn't even want Cousins playing in preseason lol.
If Cousins was 3-0 right now, after that monster "comeback" campaign on TV, RG3 would be this year's Derrick Rose. "Why won't he play?" is all we'd here. There would be an instant QB controversy, and WASH might actually trade RG3, making him one of the biggest douchebag trade pics and NFL history, and really tarnishing his name.
And since NFL players have more clout than coaches in some cities, he was allowed to bully his way back into the lineup before he was ready.