I'd really love to know how I got defeated.
it was 7:25 in game time, I was completely destroying there army as they kept spamming giants.
I had centre tower, I was attacking there statue, I didn't lag the whole game.
But After sending in my second wave...Defeat pops up

Any idea?

Uh...that happens...there're few reasons i think it was:
connection shut down and back up right away
weir kind of lag which sometimes happen, show no lag but actually lagging
he got his troops at the statue while ya not paying attention (not likely to happend though)
bug
hack (very low chance)
server problem
computer problem......
run out of idea....

I've been experiencing issues somewhat relevant to your problem. The match was going smooth, but spontaneously the thirty second timer runs out and I end up losing the match. I'm concluding this must be a server or technical problem.

It has happened to me once, i started my fight with someone, i told my first 2 miners to mine the gold and as soon as they reached the gold mine i got defeated? Not sure what it was about but i never lagg, my ping hovers around 90 and has been that way for the weeks i have been playing.
It has also happened to my brother (Croat1) After having around 5 miners it randomly cut out and said defeated.