Because if a future Somali government took them to court, many would be jailed and potentially billions paid out. If you get any form of government at the time and get them to sign, with the loopholes, you get off scot-free.
Read the times article i posted above and you'll get a timeline of what happened, how the contract he signed was presented to the parliament, and the effects. If parliaments are confirming they've seen the signed documents, it's not a smear campaign. Just go to 1:30 in the video OP posted for pics of the doc.
Medics have done studies on kids born in these regions with specific birth defects, the rise of certain cancers and respiratory problems that coincide with nuclear waste.
What do I gain from just blaming him ? it's astounding that with all of the relevant bodies citing his involvement, you're still hell-bent on defending a crook. Proper 68-er.