Sailboat skipper no doubt thought he was being careful....
1. He had a near miss with a dredge, only averted by the dredge's evasive action. If that didn't tell him he was possibly doing something wrong, what would have?
2. A spotlight shined down on him, from what have must have seemed like the heavens, and he decided to head toward that light. It could have been on land for all he knew. In any case, you don't want to put your boat near the source of the light! It probably won't (and hence didn't,) work out well for you. Had the crew of the tanker not been so diligent, they might have cut his boat in half, and never even realized it.
3. He's apparently been a "skipper" for a while and didn't notice (or care) that he couldn't hear his VHF while motoring (single handing at night no less!)?
4. Even after the collision, he didn't take the time to consult charts and his two GPS units to figure out where he was, and go to the nearest harbor. At the very least, to regroup, figure out what the hell he was doing wrong and change underwear. Instead, he continued 12 miles in what could have been a compromised vessel. I suspect he didn't even know how lucky he had been (and therefore, his underwear was clean!).
What gives you any indication he had reason to "think" he was being careful? Doesn't seem to me thinking was in his plan at all!