There’s two possible explanations - one - the FBI really is so utterly stupid that it wastes resources investigating people they should easily be able to rule out from suspicion - did they even check with him about whether he was in the USA on the day of the bombings? Presumably he meets people, it’d be easy to construct an alibi for the date of the bombings he was ‘suspected’ of if he has never left the USA in the past 10 years.
or two - the FBI realised they likely had the wrong man, but they decided to maintain the fiction that this lawyer might be a terrorism suspect in order to find out his business and to hunt through what would otherwise be legally privileged information about his clients. Even if he’s not a terrorist, they could use the false accusation and the false investigation to get at people who might be criminals.
It reminds me of the way that lawyers representing terrorism suspects were bugged in the UK during conversations with their clients. The police say the word ‘terrorist’ to throw out due process.
