Richard is "Ricardo", George is "Jorge", Stephen is "Esteban", but how was the jump made from names like William to "Guillermo" and from Elizabeth to "Isabela" or "Isabel"? These manes sound nothing like the other and didn't just get the "a" or "o" at the end. How did this come to be?
I wouldn't say Elizabeth is translated as Isabela/Isabel-- rather Elizabeth and Isabel are two names that share an etymological history. Both derive from Hebrew אלישבע, Elisheva, by way of Greek, Ἐλισάβετ Eleisabeth, Eleisabet and late ancient Latin, Elisabeth.
Isabel is just another variant, with the El- having been dropped from earlier medieval forms that appear in Catalonia and Provence: Elisabel, Elisavel, Elisaven etc.
The William .vs, Guillermo one is interesting.
Originally the name was Wilhelm and got mushed into Williame in Norman France, and of course on to England as William.
In the rest of France, words with the leading WI- began to be pronounced as GWI-, and this eventually became spelled Gui- to arrive at Guillaume and Guillermo.
This same WI- to GWI- variation between Norman French and the rest is the reason that English has both "warranty" and "guarantee". They both come from the same word at different times.
In all of those cases (most cases were names are being translated in European languages really) the names share a common root. In this case it is the holy Elizabeth, mother of John the Baptist.
Those linguistic shifts take years and years to form so sometimes it seems as the similarities disappear. But if you're being honest. Isabel and Elizabeth share some traits, notably with the s and the b sound. Just try to imagine that this similarities are comparable to the similarities of English to Spanish, who while sounding nothing alike share a common history and common roots (even though this is a bit misleading in this special case because Elisabeth/Isabel comes directly from Latin, while English and Spanishs same roots are older than Latin)
/e to clarify : The names are actually not being 'translated', it's the same name in a different language, really. But at some time those names seperated and are not being seen as identical (you wouldn't call a girl from Spain names Isabel Elizabeth when she's coming to England anymore)
Intriguingly, Isabella is not the Spanish spelling, but Italian. The Spanish name is Isabel. It'd be interesting to know why the English language "translates" the Spanish name to an Italian one, rather than the English spelling Elizabeth, and why this only happens to Spanish queens/noblewomen.