Radical fundamentalists, I believe they're saying, make more palatable enemies. Same essential reason why Hamas was funded by Israel to split Palestinian support from Fatah - Fatah, as a secular and nominally leftist organization drew some international sympathy - Hamas, much less.

The other side of the coin is that Hamas was able to rise in the first place because Fatah had become incredibly corrupt and inept.

In 1982, a prominent Israeli strategic analyst, Avner Yaniv, coined the term “Palestinian peace offensive” to describe the risk that Palestinians would become too moderate politically and Israel would be forced to make concessions.

He urged using the "fiercest military pressures" against the PLO in Lebanon to undermine Palestinian moderates and make the PLO more hardline in order "to halt its rise to political respectability".

https://www.newarab.com/analysis/why-israel-has-strategic-interest-escalating-violence

Because fighting fundamentalists gives you more international sympathy and support.

https://www.timesofisrael.com/for-years-netanyahu-propped-up-hamas-now-its-blown-up-in-our-faces/

It was also to prevent there being a unified Palestinian government by driving a wedge between the west bank and Gaza.