That's probably the case. COVID did a number to Nintendo's marketing department, and I honestly wouldn't be surprised if it - and the stay-at-home order - caused delays within the development teams.
Yes, Sakurai did state that things were going well back in late April (IIRC), but I wouldn't be surprised if small delays here and there have simply accumulated over the months.
It's worth pointing out - and emphasizing - that Nintendo's historically kept most of the research and development teams in Kyoto / Tokyo*. As such, they've probably never had the same need to build the same kind of cloud / remote working infrastructure that other companies (Microsoft, Ubisoft etc.) have built up over the past decade. The sudden need to A) build up and maintain cloud working infrastructure within Japan and B) having a workforce that's probably not used to working via the cloud transition to it probably caused delays by itself.
I'm going to go against the grain here, but personally I don't mind the wait that much. Quality first and foremost, IMHO: I don't want to imagine Min Min releasing earlier - with possibly even more bugs than the T-Pose glitch. Or Joker for that matter, since he had the glitch with Pokemon Trainer that filled his Rebel's Gauge meter really quickly (and got Joker + PT banned in doubles until a patch fixed the glitch).
So yeah, it's best to give Sakurai and co. the time they need, even if FP2's sales have suffered so far.
*" Nintendo Software Technology (NST) and Nintendo Technology Development (NTD) are located in Redmond, Washington, United States, while Nintendo European Research & Development (NERD) is located in Paris, France, and Nintendo Network Service Database (NSD) is located in Kyoto, Japan."