My bad ,read your question too quickly..
The GCU is monitoring that the IDG voltage/frequency is good among other things before the gens can be put on bus..
One is that the voltage must be stable for at least 20 secs...
Since your EGT redline still showed it means you tried to put the load on before your engine was at idle.
If it wasnt stable at idle (egt red line on) it couldnt have had 20 sec of stable output so you couldnt connect them.
Now my question is why would you try to put the gens on bus before the engine reached idle in the first place?