！？
So the first low kick was a setup for this, huh?!
Literal
1-st [possessive-の] low-kick [topic-は] this [possessive-の] setup-stone [is it-か]!?
Martial arts / fighting commentary. 布石 (ふせき) is literally 'laid stone' — originally a go (囲碁) term for a stone placed early for a later strategic purpose — used idiomatically for 'groundwork, a move laying the stage for later action'. Perfect for the 'the first move was a setup for this' revelation moment. The sentence-final か with !? expresses exclaimed realization.