Electrical – Dimmer burned and the breaker tripping on an existing LED circuit

Let me try to explain this the best I can:

• I have a single recessed LED circuit that has 13 lights on two dimmers, 9 on one and 4 on another, covering kitchen and dinning, respectively, on a 15 amp breaker. It was working no issues for about 8 years
• I also have two other led circuits with each having 6 lights on dimmers, one in living and other in family rooms.
• I found the plastic sleeve into the panel, that hold the wires, for the liv/fam rooms were lose. So I opened the panel and discovered that the circuits are connected to the same 15A breaker (two circuits one breaker).
• So I fixed the issue by adding another 15 A breaker, resulting in three circuits (kitchen+dinning, living and family) for three breakers (all 15A).
• When I was doing above I had to pull the wires from all three breakers out and rearrange them, since they are badly tangled.
• When I turned on the Kit/Din breaker, I heard a loud pop and the the dinning room LED lights (second dimmer in the circuit) would not come on, but kitchen LEDs came on when dimmers are operated. The breaker did NOT trip.
• I checked the dimmer for dinning and it was burned at where load side wiring is. Tried again with a new dimmer and same results. Btw, I really took care to follow the wiring diagram and the old wiring (took a pic)
• I removed the dimmer and circuit for dinning and turned on the breaker. Now the breaker tripped and would not stay on.
• I checked the wiring that I could see in the panel and behind the boxes of dimmers and all seemed to be fine.
• Unable to find the issue so shut the circuit (kitchen/dinette) off, at the panel.
• I took care to do the wiring correct from dimmer to line/load/neutral/ground. The panel connection have been checked many times and all good. The panel is old Federal Pioneer. The breakers are existing ones that was working fine. I even changed the breakers that I knew for sure worked fine.