Let’ try to understand why Moon gets debilitated in Scorpio sign and in Vishakha Nakshatra. Let’s see what these energies represent –

Moon - Moon represents Mind, Emotions, Mother, Local Government, Peace of Mind, Home Environment, Water, Milk etc.

Vishakha - Vishakha is nakshatra of counselors and guides. It is also nakshatra of split or partition or different direction. For more information on Vishakha Nakshatra, please check this link - https://www.astrosaxena.com/vishnaksh.

Scorpio - As Vishakha is a part of Scorpio too, Scorpio sign and its representations also become important. Scorpio is the 8th sign of zodiac belt, hence it represents the things and energy related with 8th house of horoscope like Sudden Events, Secrecy, Dark World, Occult Science, Research, Inheritance, Serving Others, Taxes etc. Besides these things sign of Scorpio also represent transformation, means changing the whole nature upside down. This is one sign which is favorite of every Astrologer, because it has maximum secrets, so every astrologer gets maximum scope of researching. This is sign about which no one can tell with precision that what will happen to the planets in it, as it is sign of secrecy itself. Wherever Scorpio falls in your chart, you may have had biggest challenges in making things related with that house more stable. Scorpio is also one of those unique signs which has 2 rulers, i.e. Mars and Ketu. In Western Astrology, Pluto also co-rules Scorpio. All this makes Scorpio a chaotic sign. Scorpio consists of next set of 2 and half nakshatras, i.e. Vishakha, Anuradha and Jyeshtha.

Please go through the introductory article 

- https://www.astrosaxena.com/exdeb .

Reasons behind debilitation of Moon in Scorpio– Basically, Moon represents our Mind and Scorpio is the sign of instabilities, changes and ups/downs in life.

Mind never wants to live under fear or uncertainties of life. We always want to be in convenient positions in life. Even a thought of any instability or a change brings a reaction from mind which wants to resist that change. It is understandable too because if your time and energy is only going to deal with instabilities of life then when you are going to utilize your time and energy to do something meaningful and productive in life? As Scorpio is sign of instabilities and changes, it is obvious that Moon will feel debilitated or weak in the sign of Scorpio.

Reasons behind debilitation of Moon in Vishakha – Now, Scorpio consists of Vishakha, Anuradha and Jyeshtha Nakshatra. Why Moon is debilitated in Vishakha Nakshatra only?

Vishakha means Two-Branches and it is also represented by forked branches going in different direction. It indicates towards split paths or directions of life. Moon is Mind. The biggest trouble our mind feels when we are going through major chaos or instability in life (Scorpio) and then we are required to take an important decision of life which can go either ways. As Vishakha represents split directions in life, Moon in Vishakha Nakshatra can make a person to get into situation again and again where he can be confused on which life path he should follow and which life path he should avoid. Hence, Moon is weakest at Vishakha.

Why Moon is debilitated at 3 degree of Vishakha Nakshatra in Scorpio sign? – It is because only the last Pada of Vishakha Nakshatra falls into Scorpio sign and as Moon is exalted at 3 degree of Taurus, it is obvious that it should be debilitated at 3 degree of Scorpio, i.e. 180 degree opposite of its exaltation degree.

Conclusion – As I see, these are the reasons why I feel Moon is debilitated in Scorpio sign and Vishakha Nakshatra at 3 degree.