Obviously we'll never know, but whilst I appreciate the "eight year commitment" claim, I feel like cutting down from four more seasons to just one probably wasn't a decision based solely on that. I strongly suspect there were other factors, particularly the political riskiness of Andor and/or (lol) its expense.
I don't know if I really buy that. Thrawn is a nothing-character in Ahsoka, they completely fail to convey his menace or even really the nature of the threat he poses, because they had to plot-armour the characters too much (and to be fair, his threat is kind of one relying on his own plans having plot armour, which is sort of incompatible with the goodies having too much). And none of the other characters involved in it seem at all important to future SW (also, Filoni seems to be incapable of extracting good performances from them).
I think it's almost entirely down to not pissing off Filoni. Ahsoka, despite being pretty bad, is clearly a pet project for him, and he's involved in the Mandalorian and de facto very heavily in future of SW (especially on the small screen), and Disney seems to have hopes he'll long-term revitalize the franchise.