The late Safety Car prompted a flurry of activity, with Valtteri stopping for fresh UltraSofts and Lewis making a late call to stay out.
At the restart, Valtteri took the fight to Lewis but was unable to get through, before the difficult call was made to hold station to the finish.
"At that stage of the race, chaos broke loose out on track," Toto said, on the Safety Car period. "It was very difficult to make the right call.
"At the end, between various voices over the radio, he [Lewis] made the decision to stay out - which was good for us, because we were splitting the bets and that proved to be the right call.
"The decision later in the race when they started to battle each other on the restart, fair enough. It was still raining in places, still humid and after so much bad luck in recent races, the scenario of losing a car or two was something we didn't want to envisage.
"If it was the other way around, we would've made the exact same call. It was important to score the one-two in order to recover some of the points which we have lost through bad luck. It was about bringing the result home."