A union derives its bargaining power from the amount of monopoly it has on the labor supply. (I don't say that as a bad thing; I mean it just as a factual thing.)
Tech industry turnover is around 13% per year, or 0.25% per week. The Google union could all quit at once and it would be like that week's turnover number was slightly higher than normal.
Google has more employees out sick on any given day than they have union members.
It took decades for America to ruin the idea of unions, they’re not coming back overnight.