While that is a possible chain in the "why this rule is or isn't in place" your usual myopia is noted. Bush isn't the only president we ever had before -- were you aware of that? There were oil and gas rigs operating in the Gulf of Mexico long before W ever showed up on the political scene, either in Texas or in Washington.
Do you have evidence that the Bush admin had any hand in removing such a requirement for ocean drilling? If so, then good, a related causation, and a black mark (an oil slick, even) on that Congress and Administration. If there had never been such a requirement in the first place, then you've got about forty to fifty years of Congressional oversight and environmental oversight that is lacking.
ETA: Dragoonster posted a snippet from WSJ that discussed US regulators deciding NOT to require these types of safety valves around 2001 or so. Your complaint in re Bush and the Congress listening too closely to the oil industry seems to be on firm groud.
We've have non-trivial restrictions and regulations on petrochemical exploration, and exploitation, both on and off shore, for decades in the US ... to include the infamous restrictions off the coast of Calfornia that dates to the 1970's.
And much else.
However, to not apply a best practice --if the reason for not using the fail safe device for a deep, deep rig was cost -- puts BP (British Petroleum, who drill all over the globe) and who make considerable noise about how environmentally strict they are, right in the spotlight for well deserved reasons.
DR