What prevented the high-paying SV companies from just opening offices in low-cost countries before the pandemic? From my point of view people who establish hiri

What prevented the high-paying SV companies from just opening offices in low-cost countries before the pandemic? From my point of view people who establish hiring process in those companies guarantee their job-security by leetcode-style interviews with some "cultural fit" sprinkled on top. People outside of SV-bubble (e.g. all your normal devs, including very smart ones) are not accustomed to reversing AVL trees on whiteboard in 20 minutes and preparing stories from their previous jobs according to STAR.