The claim " conversion from energy to matter" is not 100 % correct even though it is widely used also in serious scientific publication
Matter ( or better mass) and energy are the same stuff
They are , so to speak,the two sides of the same coin
This is the true meaning of the famous equation E = M*C^2

Moreover Quantum Physics has completly revised our concept of vacuum which was normaly undestood as synonimous with "nothing"
Consequently also the term "creation" must be revised

Suppose that you measure the electro magnetic field in volume V1 over a time T1
V1 and T1 are basically the dimension and the response time of your measuring instrumnet
You find E1 = 0 and B1 = 0
Now you try again using a more sophisticated instrument with V2 << V1 and T2 << T1
you find E2 != 0 and B2 != 0
You come to the conclusion that the electromagnetic field was not null rather the sensitivity of the instrument was too poor to measure it
Nevertheless common sense and classic physics assume that it makes sense to speak of a true " null field "
Quantum physics disagree
The field is never null rather it is " fast changing "
This is valid in general , not only for the electromagnetic field

Consequently what you call " vacuum " is actually a region of space full of energy
Since energy and mass are equivalent items than vacuum is also full of "matter"

The existence of the so called " virtual particles and anti particles " has been proved beyond any reasonable doubt
The term " virtual " may be deceiving
Acually they are "real" particles the only difference with the normal matter, being the life span which is very short

A reasonable but still unproven theory is therefore the following

" The creation(s) was(were) due to quantistic instability (ies) of vacuum "

If this theory is true , obviouly there is a little room left for a personal or impersonal God