Without seeing the bearings and crank I'd only be guessing, so take it for what it's worth....
There are about a half dozen reasons big end bearings fail. They range from improper machining of the parts, improper assembly, normal high mileage use, lack of lubrication, and debris in the oil.
Since you had an 05'? I think it's safe to assume it wasn't machining or assembly and you didn't state your mileage (that I recall, but I'm old) but unless you were 200k+ we can probably rule that out as well.
So, the two things that come to my mind are debris in the oil and lack of lubrication. Both of these are pretty easy to spot on a bearing surface. Debris in the oil makes the bearing surface look rough or scored. You can see depressions or grooves on the inner surface where the crank rides. Lack of lubrication deforms and discolors the bearing and crank. Almost like it smooshes the bearing, changing the color slightly and sometimes even makes it "shiny".
Again, both of these are two totally different looks for failure.
Debris in the oil is very likely especially if your running something like a K&N filter. Even changing the oil at specified intervals. If you drive a lot in dusty conditions and that dust gets into the oil it doesn't take much to mess up the bearings. It's even more likely if you drive "hard" in dusty conditions due to the oil filter going into bypass and allowing oil to circulate unfiltered more often for short periods of time.
OR.....It could have just been one of those days where the planets, moon, and stars aligned against you and something just decided to "let go"....It happens...
I don't know for sure about the 4.7 as I've never had one apart, but some motors you CAN replace the bearings with the motor still in the car. It's not the "best" way (and kinda "backyardish" if you ask me), but we've done a few bearing replacements in some high mileage trucks just to buy the owner some time before buying something new.
So the big questions now since you sold the WK is....Whatcha gunna buy now?!?!