There’s no time now to protect the cutting point at “a”, nor is there time to make the excellent splitting placement of W“b” on the right side, because either would allow B“c” to attack the still baseless 3 White stones in the lower left.
The urgent play is for White to immediately stabilize those 3 weak stones by providing them with a base via the two point third line skip of W1, even though that allows the strategically big B2 on the right side, with global advantage to Black.