You loaded too much hot charcoal for a low temp smoke. The amount of cold charcoal doesn't matter.
I load my charcoal basket full regardless of my desired chamber temp. I bury the chunks in the charcoal. No wood on top. Burying the wood preheats it and gives a cleaner burn. If any charcoal is left over after the smoke, reuse it.
With KBB, that I used for decades before switching to RO Ridge, I'd fire up no more than 1/4 large chimney to add to the center of my pile for 225F smokes. I eventually developed the technique of keeping the lower vents all closed, top vent full open, then go do something for an hour. When I come back, the temp is usually in the 190-200 range. When the smoke is clean, which happens before 90 mins, load the meat even if you're not at your desired chamber temp. Reset the lower vents 1/8th to 1/4 open. The temp will rise and you can make slight adjustments once temps stabilize.
You've got the hot n fast load nailed!
If you ever try RO briquettes, fire up no more than 8-10 briquettes to add to the cold charcoal. RO is 25% denser the KBB, retaining more heat energy for a longer time. Same vent/coal/load technique.
BTW, there are as many startup techniques as there are
WSM pit owners.