So easily done ... Controller should never have been fired.
Callsign confusion happens and is so common these days.
Qatar was particularly bad for similar callsigns in the same bit of airspace at the same time ...
He should have been expecting an issue here though ... but easy to judge from here. I've been stung by a similar situation where an aircraft took another a/c's clearance to be his own - even though it was a climb and maintain instruction and he was descending! Q241 v Q421 .... deep joy.