Two thoughts... It was blowing gale force. No one should be out there on purpose. We knew the front was coming days before it hit. Second is that 11' seas in the gulf are a short chop with square waves; brutal.
If that boat wasn't sound (the main leads me to believe it wasn't) then the stresses on the hull
from the square waves could have caused a breach of some type.
My guess, and only a guess, is that he couldn't put the boat into the wind
in order to drop the main.