Which doesn't actually seem to have amounted to an enormous amount, if successful prosecution is used as an indication that compelling evidence has been amassed.

Go back and read again what I wrote in the context of Don Firth's first paragraph Kevin. The evidence gathered may not secure convictions, but it does fill in parts of a jig-saw that certainly refutes Don's contention.

The man acquitted knew Atta for how long Kevin?

How long had Atta's fellow cell members been in Germany Kevin?

How were they financed and to what degree Kevin?

Where did they receive their training Kevin?

Germany is certainly not the cheapest country to live in for three years.

Would a visa application for the US from Atta, the student, resident three years in Germany be viewed equally with an application from Atta, the student, resident in Gaza for three years?

Time in planning - at least three years
Living expenses for 19, possibly more.
Tuition fees for those posing as students, I don't believe that university education is free for foreign students in Germany - maybe Wolfgang could enlighten us.
Establishment of bona-fides for the students in order that they would be accepted.
Surveillance operations at US East coast airports and onboard domestic flights once the target flights had been identified.
Travel to America, plus living and enrolement fees for their flight training.

All of the above costs money and requires a great deal of organisation Kevin - That is not what Don was trying to put across in his post.