I suspect the reason he got so much cash was that the teller probably pulled their limit (typically 3 to 5 thousand) from the CDU. I know other banks that train to pull less than $500 in actual cash to limit and make loss predictable. In reality the teller will sometimes panic and pull their limit, particularly if instructed to do so. I've never heard of anybody complaining about this happening so the teller likely won't face any problems for potentially not following the SOP. Branch will probably get a full staff retraining on robbery procedures in the next 30 days and likely additional post-robbery security protocols may be implemented. This can include the posting of uniformed guards, surveillance on the branch to audit compliance with security SOPs, increased live video monitoring, increased law enforcement activity in the area, regional investigators being around for a few weeks managing all the post-robbery activity.
The decoy is designed to look like a substantially big stack of bills. It doesn't require a lot of real cash to fluff it up. They are taught this but in the moment things don't always go according to plan. You have to trust the people going through it to know what will sell it to the bandit.
EDIT:
Regional investigators are almost exclusively former law enforcement. They tend to be highly skilled and as they are privately funded they can be applied in a sustained way the police often will not be able to. The banks can afford to make things into projects. There is also an unspoken understanding that no one will admit to if asked that they will have buddies they can call who will CPIC people for them and give out insider info to. Get involved in a security incident with a bank and you are probably getting CPIC searched with the results somehow getting back to the bank. It's routine. There are also established intelligence sharing relationships between all the banks through the Canadian Banking Association and then the individual banks and the RCMP, CSIS and the US Department of Homeland Security. Get on their radar and you are courting the Eye of Sauron.