The display cables were extremely different.
This is because the displays built into the iBook clanshell series were handled by three different vendors (to keep up with consumer demand), and all three vendors used different connections on the cable to the display itself.
Most common among these three were the Samsung display connector. This connector differed from the second-most common display, supplied by IBM. The least common of these was the LG display, whose cable connector used the same 20-pin LVDS connector found on later, higher-resolution displays. Apple supplied three different cables for these three different displays. The spare part from Apple for this LG cable connecting end (or, for that matter, the other two variants) has been unavailable for an extremely long time.
If you’re merely swapping one iBook clamshell display for another in the iBook clamshell series, then it’s important to verify that you’re sticking with the same manufacturer of the display so that the display cable remains compatible. With my own iBook clamshells, most have been Samsung-based, and one was IBM-based. You should be able to use a utility like SwitchRes X to find which manufacturer your clamshell uses, or if you’ve already disassembled it, then you’ll be able to know which display manufacturer was used.
I have yet to run across any LG-based displays in the wild. The cable I used to migrate my Samsung-based display to an LG monitor on my key lime clamshell involved a lot of reading through display schematics and soldering together a kludge between a donor Samsung display connector (on the logic board end) and a donor LG LVDS display connector on the other end. I wouldn’t recommend this path unless one is really into digging through stuff and doing a lot of fine-wire soldering.