2001 Chevy Tahoe - No power - At all

My Tahoe has been sitting for a while. I’ve cranked it up every now and then. Sometimes with a battery charger. I’ve used the car around the property a few times last three years. I’ve started to maintain the car, and change a fan control regulator.
A week or two later I tried to start the car again, but the battery was drained, so I used a battery charger. I connected this to the battery and tried to start using the charger booster. The car cranked, but didn’t start and the battery charger stopped working. Considering the age of the charger it didn’t surprise me.
I then tried to jumpstart the car with cables and another car. The Tahoe cranked over and started. I got out to disconnecting the starter cables. A few seconds later the Tahoe stopped. And I observed a small stream of smoke coming from the alternator.  I suspected the alternator had fried this due to usage of some sticky stuff used for spraying the belt to stop the wyning.
I replaced the alternator with a new one. Took the battery out and charged it with a new purchased battery charger. As I wasn’t familiar with the new charge I didn’t recognize that the battery didn’t charge.
The battery I fairly new. 2 yo. Expensive brand $ 190. Acid in all the cells all at the same level. I realize that the battery could be caput. Even if it’s not used to any extend.
After installing the battery again, there is no electric power what so ever to any systems in the car. Even at low voltage the radio display should give a sign of life. Turning the ignition key does not result in anything. No lights in the dashboard, no pling, no alarm on/off, no central locks etc. It’s the same result as if there is no battery in the car at all.
I’ve checked all battery connections positive and ground.  I checked all electric connections that I can find. No corrosion or bad wiring found.
It’s seems like the “main switch” is turned off, or a burnt main fuse. I don’t think the car has neither one.
I tried connecting the battery charger directly to the battery wires, without the battery connected. The battery charger doesn’t light up, and it’s the same result as before.
Any good ideas of what the problem is???