1. No consensus whatsoever. The Navy's orders to Capt. McVay were to "zigzag at (his) discretion, weather permitting." These orders are equivocal, and when the Indianapolis was sunk, he was not zigzagging. The prosecution said that McVay should have been zigzagging. However, the commander of the Japanese submarine that fired the torpedoes testified at the court martial that zigzagging would have made no difference. That Admiral Nimitz immediately remitted McVay's sentence and he served until 1949 tells you what the commander of the Navy in the Pacific thought of the outcome. McVay was also the only commander to lose his ship in combat during WWII and be court-martialed for it. He was completely and legally exonerated by the Navy in 2001.

As far as who was to blame, that pretty much falls squarely on the shoulders of Commander Mochitsura Hashimoto, the captain of the submarine that sunk the Indianapolis.

2. A mix of bad luck and incompetence. When the Indianapolis was sunk, she maanged to get off distress messages which were received by three stations. One station commander was reportedly drunk. A second had given orders not to disturb him while he was asleep. The third, suspecting a Japanese trap, took no action.

"But the ship was due to arrive at Leyte on a certain date," you may say, "why wasn't anything done when she didn't arrive?" Well, that's where things get a little confusing. Ships' movement were kept track on at a number of different locations: in Indy's case, the base at Leyte; the base of Commander, Marianas; and Commander Philippines. As movements for larger ships was assumed to be "on time", the latter two stations took her off the movement board at the scheduled time of arrival since they had heard nothing to the contrary The man in charge of the movement board at Leyte, however, knew immediately that the Indy was late... and did nothing about it. After all, it was hardly uncommon for ships to be delayed for any number of reasons. The correct response would have been to have reported the lateness up the line. The first the Navy officially knew she was missing was when survivors were discovered in the water three days later.

3. It actually was fairly well-known, particularly when Cmdr Hashimoto was called to testify against Capt McVay; this was the first time an enemy had appeared in court against a US office, and was considered quite controversial. Of course, the US press had a field day with it, even to the point of objecting to the cost of bringing Hashimoto to the US and putting him in a hotel (about $1800).

Sources:

Abandon Ship! - Richard Newcomb

In Harm's Way - Doug Stanton

Sunk: The Story of the Japanese Submarine Fleet, 1941–1945 - Mochitsura Hashimoto (yes, the same)

Left For Dead - Pete Nelson & Hunter Scott

USS Indianapolis.org