I had an impression that they hired lots of people at very high salaries to build fast and establish a presence all over the world.
Now that they have something nice built and are all over the world, it's a great time to cut costs. A lot of the people they've hired probably have some equity and so they're probably just fine getting laid off after the IPO.
The last few years both companies give out stock grants every month after 1 year so if somebody is laid off they don't lose equity because they already own the equity outright. Lyft even allowed people to keep their vested stock options for seven years after they leave.
Now that they have something nice built and are all over the world, it's a great time to cut costs. A lot of the people they've hired probably have some equity and so they're probably just fine getting laid off after the IPO.