The most likely consideration is that it no longer exists anywhere. There is no reason to believe anything to the contrary.
The Dimensions quoted are likely close but not exact.
2.5 cubits / 1.5 = 1.6666 Near but not right on the Golden Mean of 1.618.
I would guess the height and width dimension is 2.5/1.618 = 1.647 cubits or 1 cubit 14 .55 fingers.
Or possibly 1.5/1.618=.927 or 1 cubit 20.55 fingers if the height and width are taken as the correct dimension
Either of those shapes would be the most pleasing and perhaps ordained by God. Since such a shape was widely known nd preceeded the construction of the Ark, the design to the shape of perfection seems very likely
Nor is there any spiritual reason for it to exist any more.
ALL the things built by Moses were shadows of, and patterned upon, the REAL items in Heaven.
The exception was the Tabernacle, which was a temporary, portable structure for use until the earthly Temple would be built at the designated place; that Temple itself was a shadow of the Heavenly Temple.
Jesus, having nailed the blood ordinances to the Cross with His sacrifice; and having rent the veil of the Holy of Holies, has made obsolete all of the Temple furniture (and, indeed, the Temple itself: "in three days, I will rebuild...": He is our temple.) related to sacrifices, or the need for an intermediary (earthly High Priest) to approach the Mercy Seat on our behalf. He is now our High Priest, and all can openly approach Him.
Like the brazen snake on the staff that Moses was instructed to make in the wilderness later did, there is every danger that the Ark and other artifacts would become objects of idolatry, being worshiped in their own right. Indeed, we see much of that mind set already, even though the Ark has no verifiable physical existence; and to a lesser extent, we also see it in the Shroud of Turin.
God hates idolatry, and I have no doubt that he would have long since removed these items as the potential stumbling blocks that they are.
The real Ark is in Heaven, in the real Temple.