Why do XC and XL need to roughly match in an LC tank?
Collector feedback direct to the base is usually called negative feedback i.e. there is a natural inversion or a 180 degrees phase shift. This is the opposite of what is needed to make an oscillator. Positive feedback is needed hence, to acquire the extra 180 degrees needed to create positive feedback C1, C2 and L are used.

That extra 180 degrees precisely happens when the series combination of C1 and C2 produce an impedance magnitude equal to the impedance of L.