Covid-19 and Tires not Seating on Rim

Yesterday I got a call from a friend looking to borrow a bicycle for her
de-facto husband who's in his seventies. Their gym is closed due to
Covid-19 and they wanted to do some riding. She brought her bicycle to a
shop to get new tires (before asking me!) and no doubt spent $100+ on tires.

I had a spare "comfort bike" that someone had given me a couple of years
ago https://www.amazon.com/dp/B002FKV2R8 in a shed.

I hadn't ever used it and of course the tires were flat. I tried to
inflate the tires. The front tube would not take any air. The rear tire
would not seat easily, it looked like it was too big for the rim. I
thought I had it seated and inflated the tube and it seemed okay but
then a few minutes later the tire blew off the rim and the tube exploded.

Is it normal for unused tires to deform and enlarge when left unused for
a couple of years?

The tires were some sort of cheap Kenda tire but they looked brand new;
the person that gave me the bicycle because she was moving away had
obviously almost never ridden it. The rear wheel was horribly out of
true but it probably came that way (she bought the bicycle at Sports
Authority).

I had some Schwalbe tires, and the tubes were full of slime (which may
have wrecked the valve of the front tire so I discarded them and put on
the Schwalbe tires and Schwalbe tubes.