I really like the article you linked, because it gives an alternative explanation for why Israel is allowed to stay in the contest (other than "the EBU is really into genocide"):
In 2017, Benjamin Netanyahu abolished the old Israel Broadcasting Authority (IBA) – Eurovision in that year was its last broadcast. The reasons cited were financial, but commentators argue that it was a political move: the IBA was seen as too leftwing. It was replaced with Kan, the current broadcaster. Kan is more docile than the IBA – but still not docile enough for the government, which wants to it handed to the private sector. The communications minister, Shlomo Karhi, previously put forward a proposal to this effect in 2023, accusing the network of biased coverage and claiming that it spoke in a “disgraceful manner” towards members of the government. Such a body would be breaking EBU rules and would not be allowed into Eurovision.
The EBU feels obliged to protect Kan, even if that means risking the Eurovision brand. That’s what it was created for: to champion “free and independent” public service broadcasting. Running the Eurovision song contest is only tangential to that mission.
Basically the EBU is using the ESC as a bargaining chip to protect the independence of Kan. The problem with that: The Israeli government is taking advantage of that. And Kan doesn't seem to have a big problem with the actions of their government. After all even the "leftwing" IBA showed illegally occupied land in the 2017 postcards.
They absolutely should. But how to account for outside spending?
In the case of Israel the broadcaster didn't buy ads, the government did.