What fantasy? Italy starts with two destroyers and on R1 Italy saves it’s ipcs. Since you back your med fleet away that a Italian NO +5 ipcs and taking both Southern France and Greece is another +5 ipcs. That’s +10 ipcs saved from I1, +15 ipcs from Italy’s collected income on I1, and with the NO +5 ipcs that’s 30 ipcs which is enough to buy one aircraft carrier, one destroyer, and one sub. On R2 you would fly your fighters to seazone 97 to land on the new aircraft carrier and Germany would fly three fighters to Rome as scrambling protection. Italy also starts with two cruisers, a sub, and a battleship along with the two destroyers. If you united all Italians ships in seazone 97 and place the new ships in the same seazone along with the two fighters you get five fighters, one aircraft carrier, one battleship, two cruisers, three destroyers, and two subs. It’s not fantasy.
Your Italian IPCs that you spent on a navy are now pinned under air cover from the Southern Italy airbase – if the fleet moves out from air cover, it dies. Those German fighters are pinned too – as soon as they move away the Italian fleet dies. The UK never has to attack the Italian fleet to put it out of commission, and in the process ties up a large part of your airforce.
This is assuming that Italy lost NO units on I1 or UK2, and that’s a huge assumption. Realistically your fleet will be two or three units smaller than this. That’s minus one sub and one destroyer on an average game. It’s also an assumption that the UK will not have killed any of your dispersed units that you used clearing the Med, let’s call that minus a cruiser. So that’s three fantasy units right there.
Assuming the UK brings two fighters and a strat bomber into sea zone 97 from London, the Italian fleet (and a big chunk of the German air force) dies right there in sea zone 97 on UK3 85% or so of the time. The UK could bring a third fighter too – 90+%.
And again, still working solely with units present at startup or built on UK2. Placing part or all of a bid in the Med on UK1 makes this even stronger.
But heck, if you are buying fleet like that with Italy, the Allies have already won the game.