"This should be noted as the two names are substantially different, of different origin, meaning and history."
Except that the two names are absolutely one and the same in Portuguese, Spanish and many other languages which have no other traditional version of
Elizabeth. The queen of the
UK is known as
Isabel II in Spain and Portugal.
Isabel is simply a medieval form of
Elizabeth and its similarities to
Jezebel and the other names you mention are just coincidences.
The evolution from
Elizabeth to
Isabel is very easy to explain. The initial "E" was dropped (this happens in many medieval names:
Alienor >
Eleonore >
Leonor ;
Edward > Eduarte >
Duarte) and the final sound "th" was changed overtime to "l". Names are words and they change and evolve with time. Before people knew how to write, they changed even faster.
Many medieval forms of names have little or no similarity to the original Greek, Latin, or Hebrew name, but no-one questions that
James comes from
Yakov,
Ines comes from
Hagne, or that
Alice comes from Adelheidis.
The name was initially used in honour of the biblical character, who was and is known as St
Isabel in many languages. It was one of the most popular names in
Christian Europe during the middle ages, a time when people would not give their daughters obscure Phoenician or Hebrerw names. Even in Britian and
France the "erudite" form of the name,
Elizabeth, only became common in the Late Middle Ages —
Isabel /
Isabella was the vernacular form in English until then (as shown by the queens and princesses who bore that name and the numerous surnames based on
Isabella that still survive).
So
Elizabeth and
Isabella might have evolved to the point when they became seen as separate names in English that are independent from each other, but they are etymologically and historically the same name, like
Margaret and
Marjorie,
Anne and
Hannah, or
Jane and
Joan.