Now there will be information leaking that it’s Iran and Russia helped, and new type of warfare, new tech, etc, which is true. But this is basically them saying “it’s not we who missed it, it’s that the enemy became more advanced” to deflect blame externally. When you rely on a breach sensor from a border fence, a camera feed and a remote machine gun, if it gets broken you need to repair it right way, and deploy a team immediately. DevOps reacts faster to a server outage than IDF reacted to a breach of security. IDF probably thought that if anything serious breqed in Gaza, Shabak would know. And Shabak probably thought, that in worst case scenario, they had sensors and remote machine gun at the border. This reasoning might upset many Israeli, but it’s a case of complacency and the political elite loosing perspective of what is important.
Conversely (and oddly), I can't think of many downsides.
Getting another US ally embroiled in an extended war, an ally that the US currently holds more dearly than Ukraine, possibly helps in negatively effecting US aid to Ukraine and its appetite to prolong the war on Russia's side of the globe. Furthermore, Russia needs not have expended lots of its own resources to trigger such a war. And if can get more proxy millitias of the regional powers to enter the war, it'd be difficult for the US not to put its focus more on that area of the world.
If Israel isn't careful, it can find itself in a proxy conflict. I think Russias involvement in Syria and Iran is viewed professionally and not personal as far as that makes sense and for that matter.