.... or an aircraft might land on a nuclear power station or an oil installation is hit by a cruise liner or yon ammunition ship sunk in the Thames may go bang.
The list is almost endless but we just live with the risk; explosions on gas carriers are no worse than many other possibilities. The world still turns.
As far as 'flag of convenience' vessels go, this does not necessarily signify bad management and skipped maintenance. I have sailed under the Liberian flag on a well-managed, well-found and well-maintained vessel, classified by a reputable Society and with a British fully-certificated complement. Conversely I have sailed under the Red Ensign on a vessel whose decks were unsafe to stand on in several places, patching cargo tanks with Thistlebond on the seaward side while the Class surveyor approached from the shore.
Frankly. I think it unlikely that Class, terminal operators and charterers would accept sub-standard gas tankers. It's a specialist trade with, as you rightly say, huge consequences if things go wrong.
Regards,
Barry M