2 adapter plugs melting, fire hazard, clueless to why
There are a few factors here.


Kettles are high power loads, often close to or right at the limit of what the domestic socket standard in the country in question can safely supply
Items bought cheaply in china are likely to be of low quality. Your adapter looks like the "pin" part of the adapter is only connected to the socket part by pressure from the case.
The socket holes on that adapter look to be some kind of multi-standard compromise, accepting a bunch of plug types, but none of them well. 


Put it all together and you have a recipe for failure.

Such adapters are sometimes a necessary evil when travelling but I would strongly advise avoiding their use for long term or high current applications.