Its a co-workers baby... thus, as a co-worker, he probably felt the obligation to add more things to the gift... as compared to others in the office and what they may have gifted, too.
Co-workers, talk/gossip, in the office.
And this is a co-worker of your Husband, so maybe he felt that it was 'his' responsibility to get the gift, too.
In addition to what you got, together.
Office dynamics, are not always so pleasant.
He did take responsibility for gifting.
Which many Husbands just expect the wife to do it, and they have nothing to do, with it, themselves.
You both, work in the same office???
But sure, he could have... told you his thoughts, & reasoning for it and him buying more things.
Or, you can simply TELL him, and ask him about it and why he did so.