My two Lira on the chances and hindrances of this idea.... plus a general comment. While the pinnacle of the Renaissance is the time when historians let the Middle Ages end around 1500, we need to take into account that the start of the Renaissance in Italy is set in the second half of the 14th century already; this is connected with names like Giotto, Petrarca, Dante ; achievements like the dome of Florence's cathedral and the changes in societey following the Plague.
Throughout the Middle Ages, Italy is wealthier than most parts of the Christian world, they still sit on the top of the ruins of ROMA, have the first universities and they are the bridgehead towards the at this time more civilized realms of the Muslim World, the Byzantine Empire. So the key question should be HOW TO AVOID Italy being the focal point of whatever drags Europe out of the middle ages.
Three ideas:
-a stronger HRE: German-Roman Emperors are more successful in their struggle to subdue the Italian city states and funnel some of their wealth into their pockets (and northwards), but especially the cost of the effort to fight the Empire's forces (plus the connected inner-Italian civil wars) skyrockets so the arts starve.
-a strong Byzantine Empire keeps the Balkans and/or Mediterranean island: what if Eastern Rome always manages to hold the Danube or Sicily for some reason? While, if the Byzantine's make it past 1204/1453 that way obviously has even major butterflies, a world in which the trade with the Levante remains controlled by Constantinople and bypasses Italy via Sicily (and Sardinia, Corsica, Mallorca) or via the Danube through the Kingdom of Hungary to Vienna and into Germany or even through Venice which might remain an autonomous outpost... This might diminish Italia's fortunes in trade somewhat.
-dumber more successful popes. We often forget that many Popes in OTL's Renaissance were perhaps morally ambiguous, but many were also true Renaissance men, some even Humanists. What if the Catholic church of the late middle ages was more fanatic, but also more successful in expanding the Papal States, subduing Tuscany and perhaps Campania - turning Pisa, Florence and Siena, but also Salerno into intellectual backwaters...?
On the chances of other candidates:
- Spain: regardless if under Christian or Muslim leaders, if the atmosphere of tolerance in the Spanish Caliphate could have been preserved and become traditional south of the Pyrenaes, then Iberia might indeed be a candidate. If a prolonged balance of power makes war unprofitable, fragmented Muslim and Christian principalities might play a role similar to the Italian city states.
- Netherlands: the cities of Flanders and later Holland (Bruges, Ghent, Antwerp...Amsterdam, Rotterdam, Hague) are basically the Northern European counterparts to Pisa, Genua, Amalfi, Venice e.a. IMHO this region had a big footprint on the Renaissance OTL as well. Especially the freedom printers achieved there was pivotal for Europe's intellectual development.
However, what the Netherlands lack is the connection to the Mediterranean realms; their trade networks used to be in the Baltic and North Sea. If that could be somehow changed... perhaps by a more successful Burgundy connecting both seas via land and leading the traders of the North Sea to spend capital in Arles, Marseilles, Aigues Mortes... who knows.
- Germany: once again, Germany can't start the Renaissance if Italy already does so, so one of the scenarios above has to apply. Germany's city states in rivalry with the Imperial Court, the principalities and perhaps even the sacral states do have the potential to become centres of an Alt-Renaissance... similar to OTL-Nuremberg which was a massive center of arts and learning. ATL, Cologne, Frankfurt... perhaps also Aachen, Bremen and Hamburg could follow suit.
However, Germany's religious troubles are a major shoot into both feet. So for the Renaissance to last there, either Martin Luther shouldn't happen (or happen somewhere else) or the Reformation has to sweep Germany withouth much conflict, perhaps by an alternative to Charles V.
- Byzantine Empire. The problem I see here is that a strong Byzantine Empire would have its OWN Renaissance but, unless one of their rules pulls a "Justinian", it doesn't have that much of an effect on Western Europe. So the best shot for our idea is the unlikely prospect of 1204 leading to a successful and unified Latin-Graeco Empire which successfully becomes a cultural bridge with far more ties to Italy (e.a.). I am not an expert on that period so I regard that idea close to ASB.
- Ottoman Empire. OTL, the Ottoman Empire basically was for long stretches of its history a numerically primarily Christian nation with Muslim overlords and elites from both cultures. My impression is that they had been most efficient as long as it was that way. A fully Muslim dominance of its character came about by their expansion out of Asia Minor southwards after 1520.
So one way to make them a more interesting candidate for playing a role in Renaissance / a closer relation to Europe might be to prevent that dominance of the Arabs by making bad lucks fail a few campaigns. However, that is the 16th century and a bit late. On the other hand, for our project it might be beneficial if the Sultans take over Constantinople as EARLY as possible ; especially if the 4th crusade hadn't happened, they'd inherit a more wealthy city and its trade network intact ; also it might be a Christian entity very hard to swallow with luck leading to a fruitful hybrid identity reminiscient of the more positive aspects of Cordoba and Granada.
- the Muslim World in general. If they either prevent the decline of their golden age or manage to have a Renaissance of their own, renewing their interest in science, enabling secular thought and/or giving their religion a drift towards being less of a hindrance to progress, overcoming the limitations on what is acceptable in the arts, intensifying their trade in the Indian Ocean and discovering the Americas... whatever happens in Europe becomes a footnote anways.
