ST put priority to going north through Cap hill and up to Northgate (where there used to be a mall). Prepping the I90 bridge took a long time (8 years ago they shut down the express lanes, after adding an HOV to the main bridge) so far from my recall.

It was scheduled to open a few months ago but early this year they found a fault with the rail supports on the bridge that was missed as they were put in during early COVID and didn't have the ability to get them inspected as well as normal. So for the next year you've got Redmond to Bellevue with a missing link across the lake.

On the other side. I think that this month the main line from Northgate to Lynhood is going to open with several more stops so the system is expanding in a couple directions.

I completely agree that the 542 needs more frequency. Sound Transit likely saw the dip from Microsoft wholeheartedly embracing work-from-home and figured they could reuse the service hours. Remember that Metro has been suffering from a bad shortage of workers (drivers, maintenance, and operations) that they've only just started to recover from. This is important because Sound Transit contracts out operation of most of its transit service to the local agencies so Metro operates the 542, 545, 550, and others.

Hopefully now that Metro hiring and training is on the upswing Sound Transit will be able to get more bus service hours.