Competition between exchanges based on rules (e.g. paying liquidity takers versus makers) and surveillance (e.g pits versus dark pools or tape delays) has existed for a long time (think: American Stock Exchange versus NYSE versus NASDAQ) [1]. It sped up after the SEC passed Reg ATS [2].

[1] https://en.m.wikipedia.org/wiki/Alternative_trading_system

[2] https://www.law.cornell.edu/cfr/text/17/242.301