The fault presumed in the Ordination Rite in the Edwardine Ordinal was said to have involved form and intent (intent in the case of the consecrators of Archbishop Parker in 1559. Parker was a sort of bottleneck in the episcopacy of the Church of England). Form and intent have to be considered together in* ACs* condemnation of Anglican orders, since it is simple to find Rites that the RCC considers as conveying valid orders which use the same form. Anglicans often point that out.
Yes, the argument that Leo successfully made was that the words were ambiguous at best. Some rites have similar ordination Forms, but in those Rites the meaning of it is very clear.
But when Anglicans used words like “priesthood” and “eucharist” in their ordination ritual, they very clearly did not have the same meaning behind them as in other valid rites. As the Anglicans at the time, the 39 Articles and such, totally disowned the concept of a sacrificial priesthood and anything resembling transubstantiation. Basically, Leo concluded that you might as well have replaced “bishop” with “bureaucratic state minister” and “eucharist” with “symbolic commemoration of the Lord’s Supper.” Clearly not valid intent in the Form.
Even the bishop’s personal beliefs as an individual dont matter. If they had been intending to do “what the Church does” or “what Jesus did” it would have been valid, even if they did not personally believe. But they no longer believed that Jesus was the one who instituted the priesthood, and no longer intended to do “what the Church does” but rather “what the Anglican state institution does”…and what the Anglican state apparatus intended, was clearly not to confer true orders if they officially rejected the notion of a sacrificial priesthood and eucharist.
The Restoration restored less ambiguous terminology, and more orthodox beliefs, but it was too late. All the valid bishops were gone from England. And even then there were some groups in Anglicanism more puritan and rejecting of the notion of priesthood and eucharist, and others more “High Church” accepting them. And power fluctuated between the two, so you never know. At any given time the word “priest” in the ordinal could have officially meant a sacrificial priest in the interpretation of the official Anglican apparatus when the High Church folk were in charge, and at other times the Anglican institution probably just intended it to mean “minister and worship leader” in the case of the more Puritan.
When you reject the notion of the priesthood and eucharist, and then change your ritual to reflect that disbelief, you won’t have the apostolic sucession for very long. Even if the new ritual you use is ambiguous and potentially valid with the right intent.
But the mere change of the ritual itself was very telling. For if they believed the same things…they would have kept the same Form. Clearly, the reason for the change in rites was a change in beliefs. And when you change a Form specifically to reflect wrong beliefs, even if the wording is still potentially valid, the intent behind it is clearly invalid, as the intent behind the change was REJECTING the valid beliefs. And the people at the time would have been fine with that. They didnt want our kind of priests or eucharist, and changed their rites specifically to not express our beliefs, even if the wording came out merely ambiguous. What they left out, even if not necessary for validity, is also very telling about what they intended to express by changing the ritual, and how they interpretted the meaning.