I am loathe to quote Wiki.....but there is a good summary of the situation faced by Coastal Command prior to and during the War.
It points to the Air Ministry in unflattering terms and points out the lack of preparedness and strategic thought prior to the War....and a failure to properly assess the threat of the U-Boat and properly address the needs of Coastal Command re Trade Protection as a result.
Bomber Command may have been seen as the only way to take the fight to the Enemy by some.....but starving to death while doing that would have been a sad outcome of a false priority. Recall Food Rationing did not end until 1948 in the UK.
The loss of the French Fleet and German access to French Ports is what presented the Allies with a real problem and led to unsustainable losses in Merchant Shipping owing to the ease in access to the Atlantic by the U-Boats.
Once that threat was recognized, strategic plans developed, and proper priority was given to Airborne Anti-Submarine Warfare, did Coastal Command and US Forces (primarily USN Carrier forces) become effective in dealing with the U-Boat threat.
RAF Coastal Command - Wikipedia, the free encyclopedia