I think it's worth remembering three things.
1) Ittl Italy attacks after the Piave solely because irl they could have done so, but chose against doing so. Armando Diaz was very cautious as a commander precisely because he feared doing too much would see the Italian army implode irl, here he is just as cautious - but knows if France is about to be kicked out Italy must try and liberate her occupied territories to avoid poor terms. He attacks therefore, but this is not a Vittorio Veneto. The attack goes well, but the Austro-Hungarian army hasn't been annihilated - a lot of why VV went so well for example was the fact Hungary's army had already left the frontline, and Italy spent months preparing. So yeah - solid Italian victory here, but not a landslide.
The problem is that if the A-H is like OTL, well low morale aside, it lack everything else, when in OTL during the Battle of Vittorio Veneto the italian troops conquered the austrian line and looked at how little they had in term of food and equipment, the original Second Piave basically annihilated the K.u.k as an offensive force and hollowed her. Sure the Hungarian army was not there, but honestly at this stage will have make the result a little harder to achieve but never in doubt.
2) While Italy might do well for a time, one has to remember Germany still has a large, active and experienced army they could deploy to aid Austria - which would fit with German geostrategic goals. A strong Italy only benefits Germany if it is firmly allied, and the Germans had no faith Italy would switch sides after they broke the Triple Alliance. German Foreign Policy thus would dictate aiming to maintain a strong but subservient Austria - also to provide stability for the Balkans - and thus while Italy's advance is good, it is not going to be an uncontested march on Vienna.
The problem for Germany is well, she doesn't have an infinite pool of will, equipment and men and the current offensive will tire a lot of soldiers, sending them to prop up the Austrian even more will strain them; sure there will be panic because their southern front is basically open if the italians continue to advance and from Berlin pow the K.u.K is about to collapse, so their choice are to rob Paul to pay Peter. If the entente is smart will try to reinforce as quick as possible the italian front with everything they have
Plus well in honest term, Austria-Hungary is dead, even the people in Vienna knows it, they believed that any war past 1917 even if victorious will have caused the fall of the empire...once the bullet stopped due to the massive cost of the war in term of blood and treasure and by now everyone knows that the Empire is just a whole owned subsidiary of Germany, losing in this way even more legitimancy.
Sure Berlin can prop them after the war, but she will have already her socio-economic problem, there will be trouble in the east due to the russian civil war and adding also A-H will be a strain for a very tired nation.
Frankly it's much easier and cost effective for Berlin to give Rome a little save facing pittance like Trentino and the west river of Isonzo* even because they will be tired to always come to save A-H neck
Franky we are talking here at a late 1918 victory, there will be no real winner whatever the German terms will be like OTL, even because the troubles will not end with the stop of the Great War.
3) Italy by 1918 was, frankly, screwed domestically. In OTL the country annexed a vast swathe of territories, and still fell to a nationalist putsch and suffered two years of labour unrest in the Biennio Rosso. I'd say after ww1, without a miraculous far reaching victory Italy was always going to suffer a lot. The domestic situation is just unavoidable, and is the consequence of the country being almost 50/50 on whether to enter the war at all. BUT that doesn't mean Italy gets split in half, or given horrendous peace terms, or many of the other standard CP victory tropes - it just means Italy post war will not be stable and the consequences vary.
So overall, I'm not saying Italy is going to be torn into pieces, nor is it going to be completely fine. Frankly I'm actually quite pleased with my Italy lore as it's certainly unique. But I wouldn't expect the war to come with little immediate consequence for Italy, but you'll see more on that in later updates.
The real big difference here is that unlike OTL there will not be any pubblic humiliation at peace conference and the italian politicians will have an easy road to point on how the rest of the entente lose leaving them alone and so unable to win.
Will solve the situation? Not entirely as yes, troubles will be unvaoidable but it will give some breath to the liberals because...well, everybody even the socialist feared a possible A-H invasion of the nation and with the Hapbsurg Empire still existing and being a looming menace (as the one of their German masters), nobody will want to cause too much trouble due to the fear of the Hapsburg use them to launch another attack (sure not realistic but it will remain a very widespread feeling and it's very probable that an experienced politician like Giolitti will use it to mantain the government of national unity post war)
*basically what promised if she remained neutral (not that A-H ever had the intention to fullfill such promise)
