Secondly, the circumstance of an accidental collision seems very believable. Such collisions would not have been freak accidental encounters; the main mission of US attack subs at the time was to tail Soviet ballistic missile subs very closely and not be detected. The Soviet submarine commanders had some inkling of this, and responded by making erratic maneuvers to "clear their baffles" (essentially, look behind themselves, where their sonar was otherwise blind.) Trailing an unpredictable submarine very close is inherently risky. I think the blame falls on the circumstance of the Cold War itself, which compelled both sides to believe their actions were necessary.
https://en.wikipedia.org/wiki/HMS_Vanguard_and_Le_Triomphant...
not to mention quite a few more incidents of subs ramming surface vessels, which should be even easier to avoid.
2. With respect to lying about hundreds of people dying, is that really a surprise to you? Just a few possible examples off the top of my head.
RMS Lusitania, claimed to be carrying tens if not hundreds of tons of undeclared high explosives, which would have made it a 'legitimate' target for the u-boat that sank it. This is officially denied, but the Royal Navy has since endeavored to destroy the wreck and warn divers away from investigating it.
K-219, a Soviet ballistic missile sub, sank in early October 1986. Later that month USS Augusta, an American attack submarine, went in for repairs to a smashed radar dome. The US Navy denies any connection between the two.
K-129, another Soviet ballistic missile sub, sank in 1968. The US Navy figured out where it was before anybody else, claiming to have found it using sonar buoys and Bayesian search techniques. A few days after K-129 sank, USS Swordfish went into port for repairs after a supposed collision with sea ice. The US Navy denies any connection between the two.
MS Estonia was a ferry that sank in 1980 when the front loading doors failed. Allegations that the ferry was being used to smuggle military hardware were denied by everybody, then the wreck was deliberately buried under thousands of tons of gravel so that nobody can inspect it.
1988, the US Navy shoots down Iran Air Flight 655. The US Navy claims it was self-defense because their Aegis cruiser misidentified the Airbus A300 as an Iranian F-14.