Houthis are winning with Iran support,when there is only 30% od shia there.
supporters of former president are loosing with Saudi Arabia,USA and Izrael support when most of population are sunni.
It means,that Houthis must be supported by vast majority of other tribes,including sunni.And in Africa it is like election really look like/except Israel/ - tribe which is popular win war.Becouse one tribe could not win war/unless they get USA,China.whatever support and others have spears or at best old rifles/
It's Middle East, not Africa, so as usual it's more complicated.
Israel and USA provide only little and covert support. Saudis are the embodiment of the Arab army meme so they would need handholding pretty much, which they aren't getting, because of it their ground forces are dependent on mercenaries of various quality, and the good ones are obviously sent to protect their long and porous border and oil infrastructure - leaving the crappy forces for offensives inside Yemen, with expected results.
Houthis are well organized since a long time, and heavily supported by Iran, which aids with training, organization and equipment. Meanwhile the Sunnis are divided, the more militant part of them is not even ok for Saudis to support because they are moderate beheaders, and they aren't more interested in fighting the Houthis than fighting the Sunni government that the Saudis support, and then there's random tribal militias who are in it only for themselves, so it's more of a deathmatch than a simple, two coalition war.
Here's a somewhat recent map to demonstrate what an unholy mess the frontlines are:
For comparison, a map from 2015:
As you can see, not much has changed, the Houthis have in fact lost a little territory, but other than that they have bunkered down in their support centers, holding them, and being a pain in the ass, because they don't have heavy forces to assault enemy positions on large scale, while the other side is a circus on wheels and is too busy not falling apart and keeping moderate beheaders in line to start making advances.