Thus White blocks the passed pawn and creates the threat of a3-a4, whereas Black has a problem with his exposed king. The game continued
With the idea of 2...cxb4 3.axb4 a5 in order to create a powerful passed pawn.
6.gxf3 would be better, although after 6...a4 White is also suffering, but now he loses on the spot.
Initiating a series of exchanges that will facilitate the advance of the passed pawn.