The objective in this turn set is to maximize the exit speed coming out of the hairpin. The straight after the hairpin is longer than the one leading into it after turn 1, therefore maximizing speed coming out of turn 3 is more important than maximizing speed heading into turn 2.
To do this, the driver must drive a line which allows the earliest acceleration point. Planning the line by working the corners in reverse (because the highest priority one is the last one), the driver would want to late apex the entry to the hairpin to allow early acceleration out of it (show by the green arrow). To carry the highest speed possible into that late apex, the line to the apex must have as large a radius as possible (the radius prior to the green arrow). To accomplish a large radius entry into the hairpin, the left hand bend of turn 2 must be entered with a very late apex, allowing the car to travel the far left side of the track through turn 2, then into a wide radius late apex for the hairpin.
This line creates a very short straight through turn 2 into turn 3. Depending on the speed of the car coming out of turn 1, the braking line through turn 2 is likely to be too short. Additionally, because of the sharpness of the hairpin, it will be easy to create understeer entering the turn from either too sharp a turn-in or not easing off the brakes smooth enough. This is a very tight corner set and a common mistake will be to brake very hard through the short straight in turn 2, jump off the brakes quickly for the turn-in to the hairpin, and sharply turn the wheel. This will create a lot of understeer, and slow the car significantly.
To maximize the speed through the hairpin, it will be important to come off the brakes smoothly, and have a smooth turn in. To set up for this, most braking may have to be done before the turn-in to turn 2, the trail braking through the turn-in, and easing up through the apex of turn 2. Entering the short little straight of turn 2 a little too slow is not going to cost as much time as entering it too fast, understeering and going wide through the hairpin, and delaying the point of getting back onto the gas. Such a mistake will cost several MPH of top speed down the following straight.
This line might be your first instinct. It carries higher speed into the corner set by taking a straight path between the two bends of turns 2 and 3. This reduces the initial turn-in, and delays the braking point. It will feel much faster heading into the turns, and that segment will indeed be faster than the fast line alternative shown.
However, that fast entry line causes an early apex on the right hand bend heading into the hairpin. An early apex pushes the car to the outside of the track early to carry speed through the initial part of the corner. After that, a very tight turn after apexing is required to stay on the track. Compared to a late apex for the second bend, this requires a slower speed throughthe hairpin, and delays the point where you can get back on the gas. This line is faster for a short distance through turn 2, but is much slower along the entire straight after turn 3.