I don’t really understand it properly but it seems that the debt repayment is pegged to future fossil fuel revenue.

Mozambique was plunged into a debt crisis when oil and gas prices fell in 2014-16, Ribeiro said, but the solutions from international lenders to bail out the country have relied on loans being repaid through future gas revenues.

So I guess they can’t not repay the debt and they can only pay it back one way.