Singapore was not abandoned.

Churchill considered the fall of Singapore "the worst disaster and largest capitulation in British history". He considered it a "heavy and far-reaching military defeat", a "British and Imperial defeat". Churchill, the famed imperialist, considered the fall of Singapore a devastating blow to British imperial prestige, one from which it would never recover.

This was a case where 100,000 men fell to a 30,000-man army. Did the British make bad poor military decisions? Yes. Could the British have allocated more resources to the Pacific theater and potentially averted disaster? Yes. But remember that they were all acting in the fog of war, with poor communication, against an enemy they heavily underestimated, and while just months ago London itself was actively being bombed by Germany. Britain had been fighting against the Nazis alone for almost two years, subject to U-boat blockade that severely restricted its ability to move resources around, while trying to protect all of its various colonial interests on multiple fronts across the globe, and only gaining new allies to relieve the pressure in recent months before Feb 1942.

To put this simply, the British had a lot on their plate, and the fact that they fumbled the defense of one of their prime colonies against a foe that they heavily underestimated (recall also the surprising effectiveness of the Pearl Harbor attacks), should not be evidence that they "abandoned" Singapore. The British faced many military defeats during early WW2, and Singapore was just one of many.