Shoghi’s critics must have thought he had betrayed his grandfather’s legacy.

As time went on, the pressures from the Covenant-breakers increased. At the same time, there were some whom Abdu’l-Bahá had befriended, but who did not take Shoghi Effendi’s leadership seriously because they thought he could never manage to govern the affairs of the Faith after Abdu’l-Bahá. These people created an uneasy situation within the Family by their negative attitude. For instance, when they noticed that Shoghi Effendi was not following the practice of Abdu’l-Bahá in attending the mosque every Friday, and that he wore European clothes, they gradually distanced themselves from the Bahá’í community.

(THE COVENANT OF BAHA'U'LLAH By Adib Taherzadeh)

https://holy-writings.com/?a=SHOWTEXT&d=%2F%2Fen%2FBahai+Faith%2F2+-+Bahai+Studies%2FAdib+Taherzadeh%2FThe+Covenant+of+Baha%27u%27llah.txt

Reason: Abdu’l-Baha presented the Baha’i Faith as a form of Islam to the people in Palestine, which is why he attended the mosque. It was Shoghi Effendi who openly declared it an independent religion. Shoghi’s critics must have thought he had betrayed his grandfather’s legacy.