How do you know that by driving by a wreck?
Certainly it will be a far more useful way to guide policy than "You don't know for a fact that all those accidents weren't caused by external events outside the drivers control." however technically true.
There aren't evil driving-fairies nudging people's elbows, and we have manufacturing and inspection regulations to keep the percentage of mechanically unfit vehicles low. That just leaves the drivers themselves holding the primary responsibility in the majority of cases.
These are all things you already knew, which makes the question disingenuous and of questionable ultimate purpose.
How exactly is that my fault?
You make no men to on of environmental factors causing wrecks.
You also make no mention of multi-car wrecks.
Clearly you live in some part of the world with perfect weather?
The original commenter can be reasonably assumed to know which accidents they witnessed could have been influenced by things like weather, and thus are not part of his assertion.
Likewise all the follow-on vehicles in multi-vehicle events are irrelevant. No mention was made because they obviously have no bearing on the observation and point being asserted. Meaning, sure, in addition to a large number of a certain class of accidents he's talking about, there are also a other classes of accidents he's not talking about, so what?
Clearly you live in some part of the world with imperfect schools? Oh was that rude and childish?