Another bike breaks in a similar place is a Pace, I forget the model, but similar in design where the frame seatube extends a long way past the top tube, I rekon if it didn’t extend through like that, and the butting on the seatube was further from the top tube, & so min insertion point that much lower for the same insertion, it wouldnt happen.
Now there is 20-20 hindsight for you.
Soma, I wasnt joking about bonding the whole thing back together, if you like riding it, then its probably worth a few quid to try.