The small nuclear reactor people believe:
1) The major business problems with nuclear reactors are caused by the time it takes to get regulatory approval rather than actual safety, actual science, or even by complying with the actual safety regulations.
2) That if they make a nuclear reactor small enough, they can get a generic regulatory approval once and use it multiple times, all while satisfying the regulations and by being safe.
3) That it will be easier to ramp up, ramp down, fix problems, and dispose of after end of life of small nuclear reactors as opposed to large ones.
#1 is probably true. It is clear that nuclear power plants take a LOT of time to satisfy the regulators they are safe, but people can and do succeed in doing it.
#2 is up for debate. A lot of people think that the 'small' nuclear reactors they propose will still be large enough to take a lot of regulatory approval for the geographic locations and they will never get a generic approval to build model 1 and ship it everywhere.
#3 is also questionable. If you have even 4 active reactors, you can probably schedule the ramping up and ramping down on a continuous schedule for maintance. But the fixing of problems may take MORE time because they are shrinking it. And a lot of people think the size they are describing will not be easier to dispose of at end of life.
If they cannot get a generic regulatory approval for use in 'most' places, it may never be a good idea to build small nuclear reactors (except on vehicles like an aircraft carrier, submarines, rockets, etc).