Mold can become unsettled very easily, which is why we don't recommend trying to commit to a remediation yourself-unless you rent the right types of equipment and are advised on the correct steps to take. Mold reproduces through sporulation. The spores, which the mold produces, can essentially travel throughout different parts of the house and exist in areas that are far less conducive to regular mold growth.
The aforementioned is how one type of mold can become ubiquitous in one type of environment-through spreading the spores. Spores can exist in dry areas, which mold couldn't usually exist in. The spores can then develop into mold once suitable factors arise (i.e. moisture, humidity). This is the reason clients will often complain of a perpetuating type of mold that seems to be routinely popping up in a household.
This is one of the myriad reasons why we advise our clients to ensure they mitigate moisture in the household.
MOLD HEALTH EFFECTS BLOG AND RESEARCH