If he has 300.000 legal euros and wants to buy bitcoin under the table, he is an idiot because many people would kill for that amount and the exchange would need to be somewhere private. You can exchange 1.000 euros for bitcoin in a coffee shop, but not 300.000. Even if everything went well, and he was able to make the exchange smoothly, he would have legal problems to spend/exchange those bitcoin in the future.
If he were a mafia member, he wouldn’t be asking here.
The other obvious possibility is that he is a troll, which wouldn’t be surprising.
I don't take OP side but i don't find your conspiracy theory logical...
Troll or not, i don't think anyone around would help him with the request.
I never said only mafia members have savings of 300k eur