Without doing any calculations, my best guess is that the 2T inductor (and microstrip) in conjunction with C16 and C17 make for a nice impedance transformer.
C18 thru C20, and the two 5T inductors make a "half wave" low pass filter, so the 50Ohm of the load (antenna) is presented to C17. The 50Ohm is than transformed to something lower by C17, C16 and the inductors so that the available voltage at the collector of Q1 is operating on a lower impedance load.
JimB