I'd be interested to know who you're talking about here. I don't dispute that this has happened, because in my time on the forum I've seen members kicked off DT for all sorts of shenanigans. Quickseller, Master-P, and TECSHARE are two that immediately come to mind, but there are more. aTriz wasn't on DT, but he was probably close to getting on it and he was a good campaign manager who ruined his reputation by not calling out a scam soon enough. I'm curious as to who you are referring to, however.
I got aTriz showing as being on DT2 (I temporarily disabled my custom list)
I'm not sure of who the OP was referring to but I can think of a few.
Escrow.ms
https://bitcointalk.org/index.php?action=profile;u=76380 escrow.ms
https://bitcointalk.org/index.php?topic=1359865.0 (arrested for fraud)
Tradefortress of CoinLenders and Inputs.io,
https://bitcointalk.org/index.php?action=profile;u=67058
Siameze (sold account used for dodgy ICO)
https://bitcointalk.org/index.php?action=profile;u=121562
Blackarrow
https://bitcointalk.org/index.php?action=profile;u=105804
https://bitcointalk.org/index.php?topic=1125552.0
The problem is that even though these people ended up having issues and scam accusations against them their prior contributions should not be ignored. That is what got them to that stage in the first place.
Businesses do fail - crypto was high risk and still is high risk.
Some of it I covered here:
Bitcointalk trolls, dysfunction and all out flame wars. Guide to the scandals.
Senior members are still people. Fortunately a lot of scammers are discovered before they reach to that level.