Why did my amp just crash and burn ?

If the amp was on and the speaker cables not tight you created an ever load of resistance to the circuit ,check the fuses first ,sometimes you get lucky see outside fuses, and inside with a volt meter  pull each one out while unit s Unplugged .

We all make mistakes ,Always make sure all cables are secured good before turning the unit on Even swapping a digital usb cable I turn everything off  first.

It doesnot take much to cause a spike or surge , that is most likely  what happene. 

Well, was the main fuse blown.

If not , then there is a other issue. Do not attempt to fix it yourself.

Just getting the chassis open is difficult, and there's nothing you can repair yourself unless you are experienced in such things.

I have some news for everyone. So, I got home and turned off the amp and all other components in the chain. Next, located the fuse drawer on the back and could not get it to open with a flat head screwdriver. Easier to just unscrew the two screws attaching the socket to the chassis. Finally got the drawer open from there. Inside there was what looked like a frazzled 6amp fuse and next to it in a small storage compartment was a spare fuse. Inserted the new one . Went ahead and connected all ICs and the new speaker cables to the amp. Moment of truth. Connect the power plug , turn on the power button. Life is back in the amp. Life is good again .

Lessons learned : Never work on installing cables in particular spade connections with power on . Ensure spades are fastened tight enough to ensure non contact now or in the future. Never rush the process. 

All worked out well. Much praise to all who contributed along the way. A great show of support I would like to reciprocate to beginner questions in the future. 

Thankfully it was just a fuse and not the magic smoke!

I am so pleased your amp isn't damaged and working again.

Yes, lesson learned.  NEVER fiddle with speaker leads regardless of terminal type while the amp is live.

In fact don't fiddle with any leads while the system is up.

I don't like spade terminals but they are near ubiquitous now. including on my Martin Logan CLXs.  There is benefit in getting them as tight as possible, short of breaking the connector inside the speaker.  I recommend sticking to fingers and not using pliers etc.  I find they loosen over time and need re-tightening every now and then.