Sorry slick, but those used in the pic were used for current carrying conductors. (way before you were in the trade)Those are designed to be used for current carrying conductors, the style in the OP's pics are not.
There are two problems with the installation.
First, and the reason for the burnt wiring, they didn't use a Buchanan crimp tool, looks like they used a Stakon tool. Didn't make a proper connection.
Secondly, to save time, they just crimped to the incoming and taped the joint, kinda like those fancy green marrettes you guys use for grounding.
That tells me the contractor was in a hurry, and trying to cut corners. Speed on splices, or back stabbing saves a ton of labour. ( off topic- this week, replaced a parking lot backstabbed plug which was about 40 years old, so it stood up to time and the elements rather well)
Even though spring type splices were available, it took many years for the engineers to upgrade their specifications.