The tufts of small branches that so often develop where limbs were pruned from the trunks of a coast live oaks are sometimes referred to as ‘tumbleweeds’. They are about the same size as an average tumbleweed. By the time the get any larger, most of the smaller stems have subordinated and died out, leaving only a few more defined dominant stems, which will continue the process until even fewer or a single new branch dominates. Such tumbleweeds, as well as stems that originated from such growth, are weakly attached to the main trunks. They often get pruned off for the same reason that the limbs that were there before got pruned off, or because they are expected to be weakly attached. If they remain long enough, they can of course develop into new limbs.
Tufts of the same sort of growth on sycamores or other deciduous trees are known more simply as . . . ‘tufts’ I bet you didn’t see that coming. They can get much bigger than tumbleweeds before they develop much distinction between the dominant and subordinate growth. Because tuft growth is innately vigorous, the leaves are bigger and coarser. Then, when the rest of the deciduous trees that produce them defoliate in autumn, the tufts retain their green foliage until it gets ruined by frost.
This big sycamore dropped its top over summer. https://tonytomeo.com/2018/07/14/nature-is-messy/ The tufts developed on the big trunks that became exposed to sunlight by the loss of the upper canopy above. The tree will naturally try to replace its top, but will also naturally be even more disfigured and structurally deficient than it already was. As the tufts develop into limbs, and the limbs get heavy with foliage, they will be very likely to break away and fall. As unpleasant as all that sounds, it is quite natural for such a mature sycamore who is so old that he just doesn’t care who gets offended anymore.