Amateur job or not, these guys still got 5.4 BTC from whomever transferred those coins to the Address they ordered it to be paid in. The problem for us is that these people got away with this and now other kidnappers are going to copy the same strategy and this is going to become the new method to get ransom money from victims.
The South African authorities will need specialized assistance from Crypto currency specialists to stop this from spreading.
I do not know where you find that address and see that balance, but even if there is 5.4
BTC this is not proof that that the family paid part of the ransom. Also the investigation is still in progress so kidnappers are not got away, but who knows what's in this story is actually true and what is not.
This is not first case where kidnappers ask ransome in cryptocurrency, and it will not be last for sure. Technology is advancing every day, and
BTC anonymity is decreasing. Three letters agencies work hard regarding this since 2013, Edward Snowden show as that in the
documents it has released.