There is almost certainly a connection but as
@Melgar points out - quite rare and it seems to be triggering a genetic susceptibility - which is for sure going to
feel like a causation, but is one step removed. I wish your partner well
@sally mercer - and if there is any compensation for this, I wish you well with that.
Digging in a little deeper (my own GP talked about COVID seeming to "shock" the pancreas in some of her patients - ie, it seems clear that the actual viral infection itself has triggered many more people into an autoimmune reaction) - of the cases studied, some have managed without insulin, so if it were me, I'd be looking into the long term studies - is it really a type-1 situation, where you are having to supply external insulin forever, or is it some kind of temporary pathology that the pancreas will recover from.
I'm going nowhere near a diagnosis with this, but if it was me (with what I know now) - I'd be looking for a C-Peptide test in about 6 months (which would show the amount of naturally-produced insulin in his system) - as well as reading everything you can about how to interpret a blood glucose monitor trace in the meantime, because by the time that 6 month test comes around, you want to be expert in being able to figure out whether it's likely or not that you (rather your partner) still has a fully functional pancreas or not.
A bad thing has happened, for sure; but this by it's nature is quite new ground, and it's complicated - type 1 and type 2 are opposite in the way that they need to be thought of - Type 1 means not enough insulin, Type 2 typically means too much. However, if your partner has had something reversible happen to his pancreas (the organ that creates insulin normally) - it could be that the treatment with insulin could mask any recovery that the pancreas is going through (that's pretty much what happened to me, so I'm not making that up).
@becca59 is totally correct - type 1 simply has to be acknowledged and managed - however - you need to be sure first that it is type 1. For me - I became increasingly confused that some of the things I was seeing could not be explained without some level of insulin in my body, but the system could only treat me as type 1 until there was proof to the contrary.
Good luck....