Yes, it is because of Jupiter’s idealism. But it’s not only the reason because mercury gets debilitated here too, I will explain it later.
We have to see that not only Venus but Mars and Moon also gets exalted in enemy houses. But why?
See house lords where they get exalted, are Venus, Saturn and Jupiter. Aren’t they mature planets? Two of them are guru and one is judge. They all understand what others need, an immature child like mercury can’t think of others but they can. But why they are thinking of Moon in Taurus, Mars in Capricorn and Venus in Pisces ?
Answer lies in their significations. But I will explain it for Venus only.
What is Pisces?
It’s a brahmin sign. Represents moksha/salvation , ocean, bed pleasures, monks, living beyond all kind material, asylum, jail, purity, feet of shri narayana.
It is the 9th sign of watery trine and most auspicious sign. The positive part is all about salvation and pure things of the universe. For such thing one should have a satvik influence on kama or desires.
For Salvation, there should be strong control on kama, without that it is not possible.
Now, What is Venus?
It is the planet of lust and love, it controls the brahma sthan in every living body. Now, love could be anything, basically material or above it. So, for salvation there should be satvik influence on this love or venus. Never forget that Shukracharaya has the divine remedy called Sanjivini. He has the power to give rebirth not jupiter but for the correct use of that power, jupiter’s wisdom is always necessary.
Venus also represents desire, passion and partner. It controls the senses and it should be strongly placed with benefic influences to use those senses for right work, the ultimate goal to get liberated. Venus finds itself more comfortable in this sign because it’s soft and sattvik nature.
First priority to get salvation is to control over senses which is not possible without a sattvik Venus. But a native with Venus in Pisces will not leads always towards spiritual success, it depends on horoscope that what influence Venus is getting in sign.
Note: Rahu is also very important for Salvation because it’s also desire of a native, and one should desires for such thing. Sattvik influence on Rahu is must.
It gets debilitated in Virgo because it’s more self centred sign. An analytical sign, Venus has nothing to do with it, but here also Venus in benefic influence makes one good business man.