The universe started from an infinitesimally tiny dot

Did it? I don’t think so. That idea sounds plain silly.

The universe expanded instantaneously

Very, very silly and a proposition that is beyond stupid. That is simply magic, not sensible at all.

The ‘background radiation’ proves the theory

No, it does not.

People drew a graph showing the expansion of the universe.

They then conjured up a wild idea. Maybe they could extend the line down to zero. Aka the universe started from a tiny ‘dot’.

The idea became fashionable. Lots began to agree with the principle.

To amplify the claim people did some maths. Lots of calculations to see if it is feasible or not. The maths demonstrated that this idea showed a lot of promise.

Sometime later, people pointed out a problem; The model falls apart when you look at the heat distribution in the universe. No problem they thought, let’s fiddle with the numbers once again. We can simply say that the expansion stopped briefly at the size of a grapefruit allowing the heat to fan out. One barmy idea stacked upon another.

In fairness I prefer the idea that godly force hand built the universe. Then sent a man down from his heavenly abode to spread his messages - once the messages were received, he flew up into outer space. No rocket nor any need for a space suit.

Big bangs, gods. There is a much better, more credible explanation for how things became how they are now.