So I recently swapped my bars on my 2004 suzuki Savage from stock buck horns to 10” mini apes. I made sure it was a good fit and all my connections were good. My pops took it for a spin down the road and about 4  miles down the road as he slowed down the bike died on him. I came down and jumped the bike and drove it back. As I was riding home the bike started backfireing and bogging down (I thought maybe from when I disconnected and reconnected the fuel line there was some hiccups in the line or something) but I made it back. I put the charger on the battery and let it get to full charge. (back story on the battery, it’s a year old and I have had it on the charger all winter, only removed it to ride a couple times.) Here is where things are weird. When I turn the key on the bike to turn the lights on I get nothing, even though the trickle charger said the battery is at max. But if the charger is hooked up to the bike/battery when I turn the key the front headlight and the front left blinker comes on but that’s it. The other blinkers don’t come on but they do work for example when I turn on the hazards or blinkers they function properly. I even tried starting the bike with the charger on but it just clicked and shut off and I had to wait a moment for the lights to kick back on after that. I checked the fuses and there all good. If you guys have any idea what’s goin on let me know! Thanks! I’ll post pictures if needed.

This all happens with or without the tank being connected

The connectors for the left and right handlebar controls affect a lot of things.......if the left one is loose the headlight, running lights, turn signals and horn can all be affected.  If the right one is loose.....the starter and kill switch can be goofed up.

It is most common for the left one to have issues.

And.....you put  on taller handlebars that are likely pulling on the wires.

This is the charger I use and left it on for the winter. I’m currently in the process of testing the battery.

OK it's a battery tender, that shouldn't have damaged the battery,but do you have a volt meter? how low was the battery voltage that you had to jump the bike to get it back home? That's why I think you might have a grounding problem , and the front lights are the only wiring with three separate connectors,one for each wire. keep in mind that the flasher is the brighter of the two filaments. the rear blinkers probably won't work without the fuel tank connected.

Pull the lens, pull the bulb, eyeball the bulb and socket, even if you replace it, eyeball the socket for corrosion.
Then go hunting for an electrical problem.