I think both of us can be right at the same time though. Just because they had problems before the SoftBank acquisition as well doesn't necessarily make what I'm saying unreasonable. There was still sentiment in 2013 when SB closed the deal that regulators would not have approved of Sprint acquiring T Mobile [0], despite the struggles going on at Sprint at the time (that you describe). Sprint was definitely putting together a bid to acquire T Mobile, WSJ reported on it [1].
As you yourself said, Sprint was _dying_ at the time of the SB acquisition, but as far as large firms go, they were far from bankrupt yet. SoftBank simply twisted the dagger and then presented the corpse to congress instead of the dying patient.
[0] https://www.theverge.com/2014/2/4/5376824/fcc-chief-reported...
[1] https://www.wsj.com/articles/SB10001424052702303293604579256...