The evidence from reputable OSINT orgs like Bellingcat is pretty-much showing evidence that this was an accident on the part of Palistinian fighters.
There are multiple videos showing a volley of rockets were launched from within Gaza (not from Bellingcat, but other OSINT groups -- Bellingcat not ready to make a final conclusion here). One of the rockets appeared to fail while it was rising - it swerved wildly and then went dark. Then the explosion happened very nearby. Of course, there's a chance the videos are fake in some way, but that's what we've seen so far.
edit: Al Jazeera believes that the rocket did not fail, but was destroyed by Iron Dome defenses, and still believes that the explosion is an Israeli airstrike. They haven't really provided any evidence of the latter, only the former. Personally I'm thinking it's possible that the explosion in the courtyard was still caused by this event even if AJ is correct that Iron Dome shot the missile down. No other major news source seems to be following up on the "iron dome" angle.
https://www.aljazeera.com/news/2023/10/19/what-hit-ahli-hosp...
Bellingcat has photos of the impact crater - it's small, much too small for Israeli airstrike weapons.
https://www.bellingcat.com/news/2023/10/18/identifying-possi...
So what it sounds like is that there was an encampment of Palestinians who were taking refuge in the parking-lot/courtyard of this hospital, the rocket failed, and some or all of its explosives and fuel fell into this courtyard and killed a large number of people.
And yes, this is fundamentally the expected outcome of waging a war in an area the size of Montreal or Pittsburgh with even higher population density. Especially since the nearest major targets are north of Gaza, and Gaza's densest area is the northern-half of the strip.
These are weapons maintained and often built in the blockaded open-air prison of Gaza, they're not exactly Raytheon products -- a certain number of failures is to be expected and failures with offensive rockets are going to be incredibly dangerous to bystanders. I wouldn't be surprised if those rockets have killed more of their own people than Israelis.
I oppose the occupation and oppression of the Palestinians, but the facts are the facts.
edit2: My opinion is that this was almost certainly an accident. Either a Palistinian rocket failed, or possibly if AJ is telling the truth the Iron Dome accidentally caused the explosion (either directly or indirectly) when attempting to shoot down the rocket volley.