Why did Isis ended up becoming the most beloved deity in Egypt?

I am guessing it has to do with her duality in both death (connection to Osiris) and life (as a mother goddess, she definitely embodied life), as well as being part of one of the most important myths of not the most important one.

But why (and how) did she become more popular than, let's say, Amun, Ra, Hathor, Sekhmet or Baset?

She did conflate with all other goddesses (although some like Hathor retained some level of individuality, so to say), what's the reason behind that? How could she embody things do different like beauty (Hathor) hunt (Satis) war (Sekhmet) water (Anuqet) and so on and so forth...?

Could we speak of henotheism? Being Isis the "all supreme" deity while some others existed indeed, and could be worshipped?