Interesting point in the timing. In general I think it's probably just growing awareness of the issue, also combined with a growing number of people in tech starting families (often quite late) and being like 'zomg why didn't I do this earlier.' Many people in tech are also fascinated with countries like Japan which are acting like a living warning to the rest of the world about fertility.

In general though I think cultural shifts often lack any clear reason. People like Musk or Gates chiming in on the issue are almost certainly effects rather than causes.