The initial nerfs were needed, CATTB was immune to HEAT/ATGMs from the front and largely immune to AP, the turret / hull sides were fairly resistant against HEAT/ATGMs.
Add to that resilience 4000+ HP and fairly good speed/agility and you go deleting stuff ≤ 3500k with the 150 mm double tap for days.
The introduction of significant bloom between shots was necessary to actually make it a short range thing, as well as reduce armour a bit to not let it just drive up to stuff (this was also pre-shipdamage from HEAT MP/ATGMs → No pen = 0 damage).
Then nerfing reload, armour, hp, damage, penetration again and again was pure overkill.