What happened/caused these 4 great evolutionary milestones

again, “want” is probably not the right word.

Try looking at it this way. Once you accept that chemicals are able to self-replicate you will necessarily have to live in world with the results of that self-replication.
The chemicals themselves don’t “want” to do anything but the “machines” constructed by those chemicals act in such a way as to bring about one of two results.

A) Behaviours that assist the continuation of the chemical code that built them
B) Behaviours that don’t

We exists ourselves, and every creature around us also, as members of group A.
Those belonging to group B no longer exist.(and probably never got started in the first place)