... blowing drivers at a certain amount of volume is normal.
The magic word is "at a certain amount of volume." Your SF Cremona could handle power up to 300w w/o clipping and is a nominal 4-ohm speaker with a factory-rated sensitivity of 90dB/2.83v/m (at 8-ohm). The drivers may not damage at the clipping power at burst but it may, especially tweeter, at a RMS power approaching its limit where the high freq. energy to which the tweeter is vulnerable. Your JR continuum 250 is rated 250w at 8 ohm and doubled at 4 ohm load. Let us assume your tweeters were damaged when pushed at 150w at 8-ohm when the amp is operated at the clipping power 300w at 4-ohm.
Now, into 4-ohm, the equivalent sensitivity becomes 90dB/2w/m (since P = V^2 / R = 2.83^2 / 4 = 2w). Converting to 1W, the sensitivity rating becomes = 87dB/1w/m (= 90 + 10 log(1/2) = 87).
Now, at 300w, the SPL = 87 + 10 log(300/1) = 111.8dB at 1m away. Assume your MLP is 3m away from the speakers. At your listening position, the SPL = 111.8 - 10 log((3/1)^2) = 102.3dB (square distance rule).
What sound level of 102.3dB we are talking about in real life. A typical SPL inside the aircraft cabin during takeoff is approximately 105dB. My question to you, OP, is that were you listening to music at a sound level comparable to sitting inside an aircraft cabin during takeoff when the tweeter blew out? Your perceived sound level may not be very accurate, so I suggest using a smartphone app like Decibel X to measure it.