These new tech companies/existing companies were not here for the first wave of offshoring engineers many years ago. basically, the product/service degraded and they brought the product/service back onshore.
It's a cycle that will repeat. Product degrades, there will be public outrage, then they will onshore the product to fix the problems caused from offshoring.
For one, many of these companies are now used to their tech teams being remote. The tools, culture, infra, etc. over the last ~5 years has all become remote which lessens the shock of going fully offshore.
Two, many tech teams in the western world are already partially offshored and have been for some time now. I know where I worked, a reasonable % of the team was already offshore in low COL countries (India, etc.). What's happening now is just the expansion of that cost saving after initial testing of the waters was successful.
Three, the quality gap between offshore teams and their western counterparts is now much smaller, and AI will be used to lessen the gap even further (along with just throwing more bodies at each problem which you can do when your salaries are 1/3rd of what they are here).
Four, many products/services now have captured markets with strong network effects, which means they can weather a heavy degradation of services with little to no loss of customers. It's called enshittification, and businesses are doing it now because they absolutely know they can, and get away with it.
I worked with some very good offshore engineers. They all left pretty quickly for a job with double the salary, or moved abroad outright to claim it. The only ones who stuck around were the ones whose poor skills kept them from landing a better job.
It's also great for productivity when your offshore team is a rapidly rotating cast. I remember being in meetings where without any announcement, half of the developers who had slowly started to get to know the project were replaced with new faces who had no idea what they were supposed to do.