Question about VEBA contributions. Currently, an insurance company (tpa) is receiving veba contributions from a group into their main bank account and then directing the money to the veba trust. Is this a legitimate arrangement? Why aren't these funds put directly into the trust? Is this a violation of ERISA?

This is potentially a violation of ERISA. However, the TPA is already a co-fiduciary of the plan. If the TPA is licensed and bonded as such, maintains a trust account, requires the funds to pass through its trust account (rather than its general account), it is not likely a violation of ERISA.
Most TPAs of self-funded health plans exercise control over plan assets: they have to to pay claims. So plan funds going to or through a TPA's account is nothing novel or sinister.
Note: Note all states license and regulate TPAs. If you are in a state that does not, there are additional issues to consider before a determination is made. In those situations TPAs don't have trust powers and legally may not have a trust account. In that situation, the employer or VEBA should have its own account from which the TPA pays claims.