Rosalind, your thyroid gland is a cornerstone of your metabolic health, so perhaps now you are getting a bit of support in that area your blood sugars have improved.
I was diagnosed with hypothyroidism a few years ago, having previously developed T2. I honestly can't say my blood sugars improved or got worse when I started treatment, but we're all different and your feeling is plausible.
One thing I did find was that each time my levothyroxine dose was increased I felt marvellous for a couple of weeks, then y symptoms moved in again, so please don't be alarmed if that happens.
It is really very unusual that a starter dose of levothyroxine to be the correct dose for an individual. There usually needs to be an increase or two over a few months.
Do you have another set of blood tests scheduled in a few weeks? Hopefully you'll be sorted soon.