alt Hacker NewsTeam lead manages the overall direction of the team (and is possibly the expert on some portions), but for an individual subsystem a senior engineer might be the expert.
For work coming from outside the team, it’s sort of upto your management chain and team lead to prioritise. But for internally driven work (tech debt reduction, reliability/efficiency improvements etc) often the senior engineer has a better idea of the priorities for their area of expertise.
Prioritisation between the two is often a bit more collaborative and as a senior engineer you have to justify why thing X is super critical (not just propose that thing X needs to be done).
I view the goal of managers + lead as more balancing the various things the team could be doing (especially externally) and the goal of a senior engineer is to be an input to the process for a specific system they know most about.
I agree, but I think that input is limited to unopinionated information about the technical impact or user-facing impact of each task.
I don't think it can be said that senior engineers persuade their leaders to take one position or the other, because you can't really argue against a political or financial decision using technical or altruistic arguments, especially when you have no access to the political or financial context in which these decisions are made. In those conversations, "we need to do this for the good of the business" is an unbeatable move.