I'll explain it to you.
We have gone out of the Champions League three times due to the referee we had tonight making the wrong decisions against us.
This referee has a long history of being against Pep Guardiola and against Manchester City.
Pep looked at this and realised every tackle, every bit of pressure will result in a free kick against us (at best).
With this in mind Pep decided to pick a team that were better at keeping possession rather than winning it back as that was the least likely to result in freekicks, penaltys, red cards against us.
He decided that due to the above it was sensible to pick Sterling rather than Fernandinho as that minimises the risks of red cards but allows Sterling's pace to keep James pinned back, thus negating one of their biggest threats.
Foden and De Bruyne were then allowed to roam up front in the hopes that this would then pull their back 5 out of position a little allowing us to exploit the space somewhat.
Hope this helps.