MJ had the perfect storm of conditions. A track that was an 11 hardness factor = fastest ever, combined with extreme heat and favorable wind conditions and he used them to the max- so much so that he went beyond his own physical limits and strained a ham in the process.
Now Bolt used similar overall conditions but with a headwind to break it anyway and basically let people know it could have been 19.10 with a legal tail wind.
MJ must know that his 400 record is far easier to reach than his 200m record was and I’m sure he’s thinking how much farther he could have gone with it if he hadn’t been injured in that very 200m race. Even so, no one is looking like breaking that one any time soon.