Answer:
The reason it failed was that despite moving onto Manhattan at the Battle of Fort Washington, Howe was arguably too passive and slow to press his advantage and break up Washington's army, pursued peace talks; with the Staten island peace conference of 1776 (delegates from congress; Rutledge, Adams, and Franklin in attendance, no deal could be reached as they were unwilling to take the declaration of independence off the table), and allowed Washington to withdraw from Long Island under cover of dense fog. Furthermore, again after the Battle of White Plains in late 1776; he doesn't pursue Washington's bedraggled, depleted force to Philadelphia to end the War (takes winter quarters); allows Trenton and Princeton to occur.
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